Import 8051 support

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@30 42af7a65-404d-4744-a932-0658087f49c3

24 files changed, 2932 insertions, 0 deletions

diff --git a/nuttx/arch/pjrc-8051/Make.defs b/nuttx/arch/pjrc-8051/Make.defs
new file mode 100644
index 000000000..5c4349fc2
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/Make.defs
@@ -0,0 +1,65 @@
+############################################################
+# Make.defs
+#
+#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name Gregory Nutt nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################
+
+include ${TOPDIR}/.config
+
+ifeq ("${CONFIG_DEBUG}","y")
+  ARCHOPTIMIZATION	= --debug
+else
+  ARCHOPTIMIZATION	=
+endif
+
+ARCHCPUFLAGS		= -mmcs51 --stack-auto --model-large --int-long-reent --float-reent
+ARCHPICFLAGS		=
+ARCHWARNINGS		=
+ARCHDEFINES		=
+ARCHINCLUDES		= -I. -I$(TOPDIR)/include
+
+CROSSDEV		=
+CC			= sdcc
+CPP			= sdcpp
+LD			= aslink
+AS			= asx8051
+AR			= sdcclib -a
+
+CFLAGS			= $(ARCHWARNINGS) $(ARCHOPTIMIZATION) \
+			  $(ARCHCPUFLAGS) $(ARCHINCLUDES) $(ARCHDEFINES)
+
+ASMEXT			= .asm
+OBJEXT			= .rel
+LIBEXT			= .lib
+EXEEXT			= .hex
+
+
diff --git a/nuttx/arch/pjrc-8051/defconfig b/nuttx/arch/pjrc-8051/defconfig
new file mode 100644
index 000000000..d40be28da
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/defconfig
@@ -0,0 +1,185 @@
+############################################################
+# defconfig
+#
+#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name Gregory Nutt nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################
+#
+# architecture selection
+#
+# CONFIG_ARCH - identifies the arch subdirectory
+# CONFIG_ARCH_name - for use in C code
+#
+CONFIG_ARCH=pjrc-8051
+CONFIG_ARCH_8051=y
+
+#
+# General OS setup
+#
+# CONFIG_EXAMPLE - identifies the subdirectory in examples
+#   that will be used in the build
+# CONFIG_DEBUG - enables built-in debug options
+# CONFIG_DEBUG_VERBOSE - enables verbose debug output
+# CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
+#   time console output
+# CONFIG_RR_INTERVAL - The round robin timeslice will be set
+#   this number of milliseconds;  Round robin scheduling can
+#   be disabled by setting this value to zero.
+# CONFIG_SCHED_INSTRUMENTATION - enables instrumentation in 
+#   scheduler to monitor system performance
+# CONFIG_TASK_NAME_SIZE - Spcifies that maximum size of a
+#   task name to save in the TCB.  Useful if scheduler
+#   instrumentation is selected.  Set to zero to disable.
+# CONFIG_JULIAN_TIME - Enables Julian time conversions
+# CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
+#   Used to initialize the internal time logic.
+# CONFIG_DEV_CONSOLE - Set if architecture-specific logic
+#   provides /dev/console.  Enables stdout, stderr, stdin.
+#
+CONFIG_EXAMPLE=ostest
+CONFIG_DEBUG=n
+CONFIG_DEBUG_VERBOSE=n
+CONFIG_ARCH_LOWPUTC=y
+CONFIG_RR_INTERVAL=200
+CONFIG_SCHED_INSTRUMENTATION=n
+CONFIG_TASK_NAME_SIZE=0
+CONFIG_START_YEAR=2007
+CONFIG_START_MONTH=2
+CONFIG_START_DAY=21
+CONFIG_JULIAN_TIME=n
+CONFIG_DEV_CONSOLE=n
+
+#
+# The following can be used to disable categories of
+# APIs supported by the OS.  If the compiler supports
+# weak functions, then it should not be necessary to
+# disable functions unless you want to restrict usage
+# of those APIs.
+#
+# There are certain dependency relationships in these
+# features.
+#
+# o mq_notify logic depends on signals to awaken tasks
+#   waiting for queues to become full or empty.
+# o pthread_condtimedwait() depends on signals to wake
+#   up waiting tasks.
+#
+CONFIG_DISABLE_CLOCK=y
+CONFIG_DISABLE_PTHREAD=y
+CONFIG_DISABLE_SIGNALS=y
+CONFIG_DISABLE_MQUEUE=y
+
+#
+# Allow for architecture optimized implementations
+#
+# The architecture can provide optimized versions of the
+# following to improve sysem performance
+#
+CONFIG_ARCH_MEMCPY=n
+CONFIG_ARCH_MEMCMP=n
+CONFIG_ARCH_MEMMOVE=n
+CONFIG_ARCH_MEMSET=n
+CONFIG_ARCH_STRCMP=n
+CONFIG_ARCH_STRCPY=n
+CONFIG_ARCH_STRNCPY=n
+CONFIG_ARCH_STRLEN=n
+CONFIG_ARCH_BZERO=n
+CONFIG_ARCH_KMALLOC=n
+CONFIG_ARCH_KZMALLOC=n
+CONFIG_ARCH_KFREE=n
+
+#
+# General build options
+#
+# CONFIG_RRLOAD_BINARY - make the rrload binary format used with
+#   BSPs from www.ridgerun.com
+#
+CONFIG_RRLOAD_BINARY=n
+
+#
+# Sizes of configurable things (0 disables)
+#
+# CONFIG_MAX_TASKS - The maximum number of simultaneously
+#   actived tasks.  This value must be a power of two.
+# CONFIG_NPTHREAD_KEYS - The number of items of thread-
+#   specific data that can be retained
+# CONFIG_NFILE_DESCRIPTORS - The maximum number of file
+#   descriptors (one for each open)
+# CONFIG_NFILE_STREAMS - The maximum number of streams that
+#   can be fopen'ed
+# CONFIG_STDIO_BUFFER_SIZE - Size of the buffer to allocate
+#   on fopen. (Only if CONFIG_NFILE_STREAMS > 0)
+# CONFIG_NUNGET_CHARS - Number of characters that can be
+#   buffered by ungetc() (Only if CONFIG_NFILE_STREAMS > 0)
+# CONFIG_PREALLOC_MQ_MSGS - The number of pre-allocated message
+#   structures.  The system manages a pool of preallocated
+#   message structures to minimize dynamic allocations
+# CONFIG_MQ_MAXMSGSIZE - Message structures are allocated with
+#   a fixed payload size given by this settin (does not include
+#   other message structure overhead.
+# CONFIG_MAX_WDOGPARMS - Maximum number of parameters that
+#   can be passed to a watchdog handler
+# CONFIG_PREALLOC_WDOGS - The number of pre-allocated watchdog
+#   structures.  The system manages a pool of preallocated
+#   watchdog structures to minimize dynamic allocations
+#
+CONFIG_MAX_TASKS=8
+CONFIG_NPTHREAD_KEYS=0
+CONFIG_NFILE_DESCRIPTORS=0
+CONFIG_NFILE_STREAMS=0
+CONFIG_STDIO_BUFFER_SIZE=0
+CONFIG_NUNGET_CHARS=0
+CONFIG_PREALLOC_MQ_MSGS=0
+CONFIG_MQ_MAXMSGSIZE=0
+CONFIG_MAX_WDOGPARMS=2
+CONFIG_PREALLOC_WDOGS=4
+
+#
+# Stack and heap information
+#
+# CONFIG_BOOT_FROM_FLASH - Some configurations support XIP
+#   operation from FLASH.
+# CONFIG_CUSTOM_STACK - The up_ implementation will handle
+#   all stack operations outside of the nuttx model.
+# CONFIG_STACK_POINTER - The initial stack pointer
+# CONFIG_PROC_STACK_SIZE - The size of the initial stack
+# CONFIG_PTHREAD_STACK_MIN - Minimum pthread stack size
+# CONFIG_PTHREAD_STACK_DEFAULT - Default pthread stack size
+# CONFIG_HEAP_BASE - The beginning of the heap
+# CONFIG_HEAP_SIZE - The size of the heap
+#
+CONFIG_BOOT_FROM_FLASH=n
+CONFIG_CUSTOM_STACK=y
+CONFIG_PROC_STACK_SIZE=
+CONFIG_PTHREAD_STACK_MIN=
+CONFIG_PTHREAD_STACK_DEFAULT=
+CONFIG_HEAP_BASE=
+CONFIG_HEAP_SIZE=
diff --git a/nuttx/arch/pjrc-8051/include/arch.h b/nuttx/arch/pjrc-8051/include/arch.h
new file mode 100644
index 000000000..b61ce916a
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/include/arch.h
@@ -0,0 +1,76 @@
+/************************************************************
+ * arch.h
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/* This file should never be included directed but, rather,
+ * only indirectly through nuttx/arch.h
+ */
+
+#ifndef __ARCH_ARCH_H
+#define __ARCH_ARCH_H
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Public Types
+ ************************************************************/
+
+/************************************************************
+ * Public Variables
+ ************************************************************/
+
+/************************************************************
+ * Public Function Prototypes
+ ************************************************************/
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C" {
+#else
+#define EXTERN extern
+#endif
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ARCH_ARCH_H */
+
diff --git a/nuttx/arch/pjrc-8051/include/irq.h b/nuttx/arch/pjrc-8051/include/irq.h
new file mode 100644
index 000000000..c0a782967
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/include/irq.h
@@ -0,0 +1,155 @@
+/************************************************************
+ * irq.h
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/* This file should never be included directed but, rather,
+ * only indirectly through nuttx/irq.h
+ */
+
+#ifndef __ARCH_IRQ_H
+#define __ARCH_IRQ_H
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+#define EXT_INT0_IRQ 0
+#define TIMER0_IRQ   1
+#define EXT_INT1_IRQ 2
+#define TIMER1_IRQ   3
+#define UART_IRQ     4
+#define TIMER2_IRQ   5
+
+#define NR_IRQS      6
+
+/* The stack for all tasks/threads lie at the same position
+ * in IRAM.  On context switches, the STACK contents will be
+ * copied into the TCB.
+ */
+
+#define IRAM_BASE    0x0000
+#define IRAM_SIZE    0x0100
+
+#define STACK_BASE   0x0030
+#define STACK_SIZE   (IRAM_SIZE - STACK_BASE)
+
+/* This is the form of initial stack frame
+ *
+ * This initial stack frame will be configured to hold.
+ * (1) The 16-bit return address of either:
+ *
+ *     void task_start(void);
+ *     void pthread_start(void)
+ *
+ *     The return address is stored at the top of stack.
+ *     so that the RETI instruction will work:
+ *
+ *     PC15-8 <- ((SP))
+ *     (SP)   <- (SP) -1
+ *     PC7-0  <- ((SP))
+ *     (SP)   <- (SP) -1
+ */
+
+#define FRAME_RETLS 0
+#define FRAME_RETMS 1
+
+/* Then a full context save area which can be indexed with
+ * the following definitions (relative to the beginning of
+ * the initial frame.
+ */
+
+#define FRAME_ACC   2
+#define FRAME_IE    3
+#define FRAME_DPL   4
+#define FRAME_DPH   5
+#define FRAME_B     6
+#define FRAME_R2    7
+#define FRAME_R3    8
+#define FRAME_R4    9
+#define FRAME_R5    10
+#define FRAME_R6    11
+#define FRAME_R7    12
+#define FRAME_R0    13
+#define FRAME_R1    14
+#define FRAME_PSW   15
+#define FRAME_BP    16
+
+#define FRAME_SIZE  17
+
+/************************************************************
+ * Public Types
+ ************************************************************/
+
+/* This struct defines the way the registers are stored */
+
+#ifndef __ASSEMBLY__
+struct xcptcontext
+{
+   ubyte nbytes;
+   ubyte stack[STACK_SIZE];
+};
+#endif /* __ASSEMBLY */
+
+/************************************************************
+ * Public Variables
+ ************************************************************/
+
+/************************************************************
+ * Public Function Prototypes
+ ************************************************************/
+
+#ifndef __ASSEMBLY__
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C" {
+#else
+#define EXTERN extern
+#endif
+
+EXTERN irqstate_t irqsave(void) __naked;
+EXTERN void       irqrestore(irqstate_t flags) __naked;
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ASSEMBLY */
+#endif /* __ARCH_IRQ_H */
+
diff --git a/nuttx/arch/pjrc-8051/include/types.h b/nuttx/arch/pjrc-8051/include/types.h
new file mode 100644
index 000000000..9656c0231
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/include/types.h
@@ -0,0 +1,87 @@
+/************************************************************
+ * types.h
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/* This file should never be included directed but, rather,
+ * only indirectly through sys/types.h
+ */
+
+#ifndef __ARCH_TYPES_H
+#define __ARCH_TYPES_H
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Type Declarations
+ ************************************************************/
+
+#ifndef __ASSEMBLY__
+
+/* These are the sizes of the standard SDCC types
+ *
+ * For SDCC, sizeof(int) is 16 and sizeof(long) is 32.
+ * long long and double are not supported.
+ *
+ * Generic pointers are 3 bytes in length with the the
+ * first byte holding data space intformation.
+ */
+
+typedef char sbyte;
+typedef unsigned char ubyte;
+typedef unsigned char uint8;
+typedef unsigned char boolean;
+typedef int sint16;
+typedef unsigned int uint16;
+typedef long sint32;
+typedef unsigned long uint32;
+
+/* This is the size of the interrupt state save returned by
+ * irqsave()
+ */
+
+typedef unsigned char irqstate_t;
+
+#endif /* __ASSEMBLY__ */
+
+/************************************************************
+ * Global Function Prototypes
+ ************************************************************/
+
+#endif /* __ARCH_TYPES_H */
diff --git a/nuttx/arch/pjrc-8051/setenv.sh b/nuttx/arch/pjrc-8051/setenv.sh
new file mode 100755
index 000000000..69614aefe
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/setenv.sh
@@ -0,0 +1,45 @@
+#!/bin/sh
+# setenv.sh
+#
+#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name Gregory Nutt nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+if [ "$(basename $0)" = "setenv" ] ; then
+  echo "You must source this script, not run it!" 1>&2
+  exit 1
+fi
+
+if [ -z ${PATH_ORIG} ]; then export PATH_ORIG=${PATH}; fi
+
+export SDCC_BIN=/usr/local/bin
+export PATH=${SDCC_BIN}:/sbin:/usr/sbin:${PATH_ORIG}
+
+echo "PATH : ${PATH}"
diff --git a/nuttx/arch/pjrc-8051/src/Makefile b/nuttx/arch/pjrc-8051/src/Makefile
new file mode 100644
index 000000000..5adb30284
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/Makefile
@@ -0,0 +1,134 @@
+############################################################
+# Makefile
+#
+#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name Gregory Nutt nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################
+
+-include $(TOPDIR)/Make.defs
+
+MKDEP 		= $(TOPDIR)/tools/mkdeps.sh
+CFLAGS		+= -I$(TOPDIR)/sched
+ASFLAGS		= -x -j -g -l -s -p
+CPPFLAGS	= $(ARCHINCLUDES) $(ARCHDEFINES) -D__ASSEMBLY__
+
+SSRCS		= 
+ASRCS		= $(SSRCS:.S=$(ASMEXT))
+AOBJS		= $(ASRCS:$(ASMEXT)=$(OBJEXT))
+CSRCS		= up_initialize.c up_idle.c up_interruptcontext.c \
+		  up_initialstate.c up_unblocktask.c up_blocktask.c \
+		  up_releasepending.c up_reprioritizertr.c \
+		  up_exit.c up_assert.c up_allocateheap.c \
+		  up_irq.c up_savecontext.c up_restorecontext.c up_putc.c
+COBJS		= $(CSRCS:.c=$(OBJEXT))
+SRCS		= $(SSRCS) $(CSRCS)
+OBJS		= $(AOBJS) $(COBJS)
+
+SDCCLIBDIR	= /usr/local/share/sdcc/lib/large
+SDCCPATH	= -L$(SDCCLIBDIR)
+SDCCLIBS	= -llibfloat.lib -llibint.lib -lliblong.lib -llibmysdcc.lib -lmcs51.lib
+
+LINKSSRCS	= up_head.S
+LINKASRCS	= $(LINKSSRCS:.S=$(ASMEXT))
+LINKOBJS	= $(LINKASRCS:$(ASMEXT)=$(OBJEXT))
+LINKLIBS	=
+LDPATHES	= $(addprefix -L$(TOPDIR)/,$(dir $(LINKLIBS)))
+LDLIBS		= $(addprefix -l,$(notdir $(LINKLIBS)))
+
+LDFLAGS		= --model-large --nostdlib \
+		  --data-loc 0x30 --iram-size 0x100 \
+		  --code-loc 0x2040 --code-size 0x5fc0 \
+		  --xram-loc 0x0100 --xram-size 0x1f00
+
+HEAP_START	= ${shell cat pass1.mem | grep "EXTERNAL RAM" | sed -e "s/[ ][ ]*/ /g" | cut -d' ' -f5}
+
+DEPSRCS		= $(SRCS) $(LINKSSRCS)
+
+all: up_head$(OBJEXT) libarch$(LIBEXT)
+
+$(ASRCS) $(LINKASRCS): %$(ASMEXT): %.S
+	$(CPP) -P $(CPPFLAGS) -D__ASSEMBLY__ -DUP_HEAP_START=0x0100 -DUP_HEAP_END=0x2000 $< -o $@
+
+$(AOBJS) $(LINKOBJS): $(ASRCS) $(LINKASRCS)
+	$(AS) $(ASFLAGS) $<
+
+$(COBJS): %$(OBJEXT): %.c
+	$(CC) -c $(CFLAGS) -DUP_HEAP_START=0x0100 -DUP_HEAP_END=0x2000 $< -o $@
+
+# Combine all objects in this directory into a library
+
+libarch$(LIBEXT): $(OBJS)
+	( for obj in $(OBJS) ; do \
+		$(AR) $@ $${obj} || \
+			{ echo "$(AR) $@ $${obj} FAILED!" ; exit 1 ; } ; \
+	done ; )
+
+# This is a kludge to work around some conflicting symbols in libsdcc.lib
+
+$(SDCCLIBDIR)/libmysdcc.lib: $(SDCCLIBDIR)/libsdcc.lib
+	@cat $(SDCCLIBDIR)/libsdcc.lib | \
+		grep -v calloc  | grep -v malloc  | grep -v realloc  | \
+		grep -v free    | grep -v vprintf | grep -v _strncpy | \
+		grep -v _strchr | grep -v _strlen | grep -v _strcmp  | \
+		grep -v _strcpy | grep -v _memcmp | grep -v _memcpy  | \
+		grep -v _memset \
+		> libmysdcc.lib
+	@sudo mv -f libmysdcc.lib $(SDCCLIBDIR)/libmysdcc.lib
+
+# This target builds the final executable
+
+pass1$(EXEEXT): $(SDCCLIBDIR)/libmysdcc.lib $(LINKOBJS)
+	$(CC) $(LDFLAGS) $(LDPATHES) $(SDCCPATH) $(LINKOBJS) $(LDLIBS) $(SDCCLIBS) -o pass1.ihx
+
+nuttx$(EXEEXT): pass1$(EXEEXT)
+	$(CC) -c $(CFLAGS) -DUP_HEAP_START=$(HEAP_START) -DUP_HEAP_END=0x2000 \
+		up_allocateheap.c -o up_allocateheap$(OBJEXT)
+	@rm -f pass1.*
+	$(CC) $(LDFLAGS) $(LDPATHES) $(SDCCPATH) $(LINKOBJS) $(LDLIBS) $(SDCCLIBS) -o nuttx.ihx
+	packihx nuttx.ihx > $(TOPDIR)/nuttx$(EXEEXT)
+	@cp -f nuttx.map $(TOPDIR)/.
+
+# Build dependencies
+
+.depend: Makefile $(DEPSRCS)
+	$(MKDEP) $(CC) -- $(CFLAGS) -- $(SRCS) >Make.dep
+	touch $@
+
+depend: .depend
+
+clean:
+	rm -f libarch$(LIBEXT) *.asm *.rel *.lst *.rst *.sym *.adb *.lnk *.map *.mem *.ihx *.hex *~
+	if [ ! -z "$(OBJEXT)" ]; then rm -f *$(OBJEXT); fi
+
+distclean: clean
+	rm -f Make.dep .depend
+
+-include Make.dep
diff --git a/nuttx/arch/pjrc-8051/src/up_allocateheap.c b/nuttx/arch/pjrc-8051/src/up_allocateheap.c
new file mode 100644
index 000000000..6a874ed2a
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_allocateheap.c
@@ -0,0 +1,79 @@
+/************************************************************
+ * up_allocateheap.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_allocate_heap
+ *
+ * Description:
+ *   The heap may be statically allocated by
+ *   defining CONFIG_HEAP_BASE and CONFIG_HEAP_SIZE.  If these
+ *   are not defined, then this function will be called to
+ *   dynamically set aside the heap region.
+ *
+ ************************************************************/
+
+void up_allocate_heap(FAR void **heap_start, size_t *heap_size)
+{
+  *heap_start = (FAR void*)UP_HEAP_START;
+  *heap_size = UP_HEAP_END - UP_HEAP_START;
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_assert.c b/nuttx/arch/pjrc-8051/src/up_assert.c
new file mode 100644
index 000000000..b9ac5db43
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_assert.c
@@ -0,0 +1,80 @@
+/************************************************************
+ * up_assert.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <debug.h>
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_assert
+ ************************************************************/
+
+void up_assert(void)
+{
+  dbg("Assertion failed\n");
+  exit(EXIT_FAILURE);
+}
+
+/************************************************************
+ * Name: up_assert_code
+ ************************************************************/
+
+void up_assert_code(int errorcode)
+{
+  dbg("Assertion failed with error code: %d\n", errcode);
+  exit(errorcode);
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_blocktask.c b/nuttx/arch/pjrc-8051/src/up_blocktask.c
new file mode 100644
index 000000000..4a15a817a
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_blocktask.c
@@ -0,0 +1,171 @@
+/************************************************************
+ * up_blocktask.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Funtions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_block_task
+ *
+ * Description:
+ *   The currently executing task at the head of
+ *   the ready to run list must be stopped.  Save its context
+ *   and move it to the inactive list specified by task_state.
+ *
+ * Inputs:
+ *   tcb: Refers to a task in the ready-to-run list (normally
+ *     the task at the the head of the list).  It most be
+ *     stopped, its context saved and moved into one of the
+ *     waiting task lists.  It it was the task at the head
+ *     of the ready-to-run list, then a context to the new
+ *     ready to run task must be performed.
+ *   task_state: Specifies which waiting task list should be
+ *     hold the blocked task TCB.
+ *
+ ************************************************************/
+
+void up_block_task(FAR _TCB *tcb, tstate_t task_state)
+{
+  /* Verify that the context switch can be performed */
+
+  if ((tcb->task_state < FIRST_READY_TO_RUN_STATE) ||
+      (tcb->task_state > LAST_READY_TO_RUN_STATE))
+    {
+      PANIC(OSERR_BADBLOCKSTATE);
+    }
+  else
+    {
+      FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
+      boolean switch_needed;
+
+      dbg("Blocking TCB=%p\n", tcb);
+
+      /* Remove the tcb task from the ready-to-run list.  If we
+       * are blocking the task at the head of the task list (the
+       * most likely case), then a context switch to the next
+       * ready-to-run task is needed. In this case, it should
+       * also be true that rtcb == tcb.
+       */
+
+      switch_needed = sched_removereadytorun(tcb);
+
+      /* Add the task to the specified blocked task list */
+
+      sched_addblocked(tcb, (tstate_t)task_state);
+
+      /* If there are any pending tasks, then add them to the g_readytorun
+       * task list now
+       */
+
+      if (g_pendingtasks.head)
+        {
+          switch_needed |= sched_mergepending();
+        }
+
+      /* Now, perform the context switch if one is needed */
+
+      if (switch_needed)
+        {
+          /* Are we in an interrupt handler? */
+
+          if (g_ininterrupt)
+            {
+#if 0
+# warning REVISIT
+              /* Yes, then we have to do things differently.
+               * Just copy the current registers into the OLD rtcb.
+               */
+
+               up_copystate(&tcb->xcp, current_regs);
+
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (_TCB*)g_readytorun.head;
+              dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_copystate(current_regs, &tcb->xcp);
+#endif
+            }
+
+          /* Copy the user C context into the TCB at the (old) head of the
+           * g_readytorun Task list. if up_savecontext returns a non-zero
+           * value, then this is really the previously running task restarting!
+           */
+
+          else if (!up_savecontext(&rtcb->xcp))
+            {
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (FAR _TCB*)g_readytorun.head;
+              dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_restorecontext(&rtcb->xcp);
+            }
+        }
+    }
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_exit.c b/nuttx/arch/pjrc-8051/src/up_exit.c
new file mode 100644
index 000000000..5a98496a6
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_exit.c
@@ -0,0 +1,111 @@
+/************************************************************
+ * up_exit.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Funtions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: _exit
+ *
+ * Description:
+ *   This function causes the currently executing task to cease
+ *   to exist.  This is a special case of task_delete().
+ *
+ ************************************************************/
+
+void _exit(int status)
+{
+  FAR _TCB* tcb = (FAR _TCB*)g_readytorun.head;
+
+  dbg("TCB=%p exitting\n", tcb);
+
+  /* Remove the tcb task from the ready-to-run list.  We can
+   * ignore the return value because we know that a context
+   * switch is needed.
+   */
+
+  (void)sched_removereadytorun(tcb);
+
+  /* Move the TCB to the specified blocked task list and delete it */
+
+  sched_addblocked(tcb, TSTATE_TASK_INACTIVE);
+  task_delete(tcb->pid);
+
+  /* If there are any pending tasks, then add them to the g_readytorun
+   * task list now
+   */
+
+  if (g_pendingtasks.head)
+    {
+      (void)sched_mergepending();
+    }
+
+  /* Now, perform the context switch to the new ready-to-run task at the
+   * head of the list.
+   */
+
+  tcb = (FAR _TCB*)g_readytorun.head;
+  dbg("New Active Task TCB=%p\n", tcb);
+
+  /* Then switch contexts */
+
+  up_restorecontext(&tcb->xcp);
+}
+
diff --git a/nuttx/arch/pjrc-8051/src/up_head.S b/nuttx/arch/pjrc-8051/src/up_head.S
new file mode 100644
index 000000000..ff2f3a5c9
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_head.S
@@ -0,0 +1,229 @@
+/************************************************************
+ * up_head.S
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/irq.h>
+#include "up_internal.h"
+
+	.module	up_head
+	.optsdcc -mmcs51 --model-large
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+	.area REG_BANK_0	(REL,OVR,DATA)
+	.ds 8
+
+/************************************************************
+ * Public Data
+ ************************************************************/
+
+	.globl	_g_ininterrupt
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+	.globl	_irq_dispatch
+
+/************************************************************
+ * Program entry points
+ ************************************************************/
+
+/* Program entry is through PROGRAM_BASE.  This is just a
+ * branch to our start up logic.
+ */
+
+	.area	CODE1 (ABS)
+	.org	PROGRAM_BASE
+	ljmp	start
+
+/* These are indirect interrupt vectors.  Logic in PAULMON2,
+ * captures the interrupt vectors (near address 0x0000) and
+ * re-routes them through the following entry points.
+ *
+ * Each of these saves acc and ie then passes the IRQ number
+ * to higher level logic in a
+ */
+
+	.org	PM2_VECTOR_EXTINT0
+	push	acc
+	push	ie
+	mov	a, #EXT_INT0_IRQ
+	ljmp	_up_interrupt
+
+	.org	PM2_VECTOR_TIMER0
+	push	acc
+	push	ie
+	mov	a, #TIMER0_IRQ
+	ljmp	_up_interrupt
+
+	.org	PM2_VECTOR_EXTINT1
+	push	acc
+	push	ie
+	mov	a, #EXT_INT1_IRQ
+	ljmp	_up_interrupt
+
+	.org	PM2_VECTOR_TIMER1
+	push	acc
+	push	ie
+	mov	a, #TIMER1_IRQ
+	ljmp	_up_interrupt
+
+	.org	PM2_VECTOR_UART
+	push	acc
+	push	ie
+	mov	a, #UART_IRQ
+	ljmp	_up_interrupt
+
+	.org	PM2_VECTOR_TIMER2
+	push	acc
+	push	ie
+	mov	a, #TIMER2_IRQ
+	ljmp	_up_interrupt
+
+/************************************************************
+ * Name: start
+ *
+ * Description:
+ *   This is the initial entry point into NuttX
+ *
+ ************************************************************/
+
+start:
+	mov	sp, #(STACK_BASE-1)
+	ljmp	_os_start
+
+/************************************************************
+ * Name: up_interrupt
+ *
+ * Description:
+ *   All interrupts vector to this point with:
+ *
+ *   (1) acc and ie on the stack and
+ *   (2) the IRQ number in the accumulator
+ *
+ ************************************************************/
+
+_up_interrupt:
+	ar2 = 0x02
+	ar3 = 0x03
+	ar4 = 0x04
+	ar5 = 0x05
+	ar6 = 0x06
+	ar7 = 0x07
+	ar0 = 0x00
+	ar1 = 0x01
+
+	/* Push ACC and IE.  Then disable interrupts */
+
+	push	acc
+	push	ie
+	clr	ea
+
+	/* Now push the remaining registers with interrupt disabled */
+
+	push	dpl
+	push	dph
+	push	b
+	push	ar2
+	push	ar3
+	push	ar4
+	push	ar5
+	push	ar6
+	push	ar7
+	push	ar0
+	push	ar1
+	push	psw
+	clr	psw
+	push	_bp
+
+	/* Now call void irq_dispatch(int irq, FAR void *context)
+         *
+	 * First, create the first argument as (int)irqno
+	 */
+
+        mov     dpl, a
+	clr	dph
+
+        /* Create the second argument (void *context) on the stack */
+
+        push    sp
+        clr     a
+        push    acc
+
+	/* Then dispatch the IRQ */
+
+	lcall	_irq_dispatch
+
+	/* Clean up the stack */
+
+        dec     sp
+        dec     sp
+
+	/* Then return from the interrupt */
+
+	pop	_bp 
+	pop	psw
+	pop	ar1 
+	pop	ar0 
+	pop	ar7 
+	pop	ar6 
+	pop	ar5 
+	pop	ar4 
+	pop	ar3 
+	pop	ar2 
+	pop	b
+	pop	dph
+	pop	dpl
+
+	/* Restore the interrupt state per the stored IE value */
+
+	pop	acc
+	jb	acc.7, 00001$
+	clr	ie.7
+	sjmp	00002$
+  00001$:
+	setb	ie.7
+  00002$:
+
+	/* Finally pop off the ACC, which was the first register saved. */
+
+	pop acc
+	reti
diff --git a/nuttx/arch/pjrc-8051/src/up_idle.c b/nuttx/arch/pjrc-8051/src/up_idle.c
new file mode 100644
index 000000000..fcc89ed9b
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_idle.c
@@ -0,0 +1,79 @@
+/************************************************************
+ * up_idle.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <nuttx/arch.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_idle
+ *
+ * Description:
+ *   up_idle() is the logic that will be executed when their
+ *   is no other ready-to-run task.  This is processor idle
+ *   time and will continue until some interrupt occurs to
+ *   cause a context switch from the idle task.
+ *
+ *   Processing in this state may be processor-specific. e.g.,
+ *   this is where power management operations might be
+ *   performed.
+ *
+ ************************************************************/
+
+void up_idle(void)
+{
+}
+
diff --git a/nuttx/arch/pjrc-8051/src/up_initialize.c b/nuttx/arch/pjrc-8051/src/up_initialize.c
new file mode 100644
index 000000000..20d2e8122
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_initialize.c
@@ -0,0 +1,98 @@
+/************************************************************
+ * up_initialize.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <nuttx/arch.h>
+#include <nuttx/fs.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/* TRUE if processing an interrupt */
+
+boolean g_ininterrupt;
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_initialize
+ *
+ * Description:
+ *   up_initialize will be called once during OS
+ *   initialization after the basic OS services have been
+ *   initialized.  The architecture specific details of
+ *   initializing the OS will be handled here.  Such things as
+ *   setting up interrupt service routines, starting the
+ *   clock, and registering device drivers are some of the
+ *   things that are different for each processor and hardware
+ *   platform.
+ *
+ *   up_initialize is called after the OS initialized but
+ *   before the init process has been started and before the
+ *   libraries have been initialized.  OS services and driver
+ *   services are available.
+ *
+ ************************************************************/
+
+void up_initialize(void)
+{
+ /* Initialize global variables */
+
+  g_ininterrupt = FALSE;
+
+  /* Initialize the interrupt subsystem */
+
+  /* Initialize the system timer interrupt */
+
+  /* Initialize the serial console support */
+}
+
diff --git a/nuttx/arch/pjrc-8051/src/up_initialstate.c b/nuttx/arch/pjrc-8051/src/up_initialstate.c
new file mode 100644
index 000000000..930f16873
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_initialstate.c
@@ -0,0 +1,108 @@
+/************************************************************
+ * up_initialstate.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_initial_state
+ *
+ * Description:
+ *   A new thread is being started and a new TCB
+ *   has been created. This function is called to initialize
+ *   the processor specific portions of the new TCB.
+ *
+ *   This function must setup the intial architecture registers
+ *   and/or  stack so that execution will begin at tcb->start
+ *   on the next context switch.
+ *
+ ************************************************************/
+
+void up_initial_state(FAR _TCB *tcb)
+{
+  FAR ubyte *frame = tcb->xcp.stack;
+
+  /* This is the form of initial stack frame
+   *
+   * This initial stack frame will be configured to hold.
+   * (1) The 16-bit return address of either:
+   *
+   *     void task_start(void);
+   *     void pthread_start(void)
+   *
+   *     The return address is stored at the top of stack.
+   *     so that the RETI instruction will work:
+   *
+   *     PC15-8 <- ((SP))
+   *     (SP)   <- (SP) -1
+   *     PC7-0  <- ((SP))
+   *     (SP)   <- (SP) -1
+   */
+
+   frame[FRAME_RETLS] = (((uint16)tcb->start) & 0xff);
+   frame[FRAME_RETMS] = (((uint16)tcb->start) >> 8);
+
+  /* Then the context save area which can be indexed with
+   * the following definitions (relative to the beginning of
+   * the initial frame.
+   */
+
+  frame[FRAME_IE]     = 0x80;
+  frame[FRAME_PSW]    = 0;
+
+  tcb->xcp.nbytes     = FRAME_SIZE;
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_internal.h b/nuttx/arch/pjrc-8051/src/up_internal.h
new file mode 100644
index 000000000..27a83585f
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_internal.h
@@ -0,0 +1,125 @@
+/**************************************************************************
+ * up_internal.h
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************/
+
+#ifndef __ARCH_UP_INTERNAL_H
+#define __ARCH_UP_INTERNAL_H
+
+/**************************************************************************
+ * Included Files
+ **************************************************************************/
+
+/**************************************************************************
+ * Public Definitions
+ **************************************************************************/
+
+/* Memory Map
+ *
+ * BEGIN  END     DESCRIPTION
+ * 0x0000 0x1fff  CODE:   ROM containg PAULMON2
+ *                DATA:   RAM for program variables
+ * 0x2000 0x7fff  COMMON: RAM for program code or
+ *                        variables
+ * 0x8000 0xf7ff  COMMON: FLASH for program code
+ * 0xf800 0xfeff  COMMON: Peripherals
+ * 0xff00 0xffff  COMMON: unused
+ *
+ * Program code may be loaded at the RAM location 0x2000-0x7fff
+ * for testing.  If loaded into the FLASH location at
+ * 0x8000-0xf7ff, PAULMON2 will automatically write the program
+ * into flash.  The program is configured in the RAM-based test
+ * configuration:
+ */
+
+#define RAM_BLOCK_START  IRAM_SIZE
+#define RAM_BLOCK_END    0x1fff
+
+#define PROGRAM_BASE     0x2000
+#define PROGRAM_END      0x7fff
+
+#define FLASH_BASE       0x8000
+#define FLASH_END        0xf7ff
+
+/* Well-known entry points to access PAULMON2's built-in functions */
+
+#define PM2_ENTRY_PHEX1   0x002e
+#define PM2_ENTRY_COUT    0x0030
+#define PM2_ENTRY_CIN     0x0032
+#define PM2_ENTRY_PHEX    0x0034
+#define PM2_ENTRY_PHEX16  0x0036
+#define PM2_ENTRY_PSTR    0x0038
+#define PM2_ENTRY_ESC     0x003e
+#define PM2_ENTRY_UPPER   0x0040
+#define PM2_ENTRY_PINT8U  0x004D
+#define PM2_ENTRY_PINT8   0x0050
+#define PM2_ENTRY_PINT16U 0x0053
+#define PM2_ENTRY_NEWLINE 0x0048
+#define PM2_ENTRY_PRGM    0x0059
+#define PM2_ENTRY_ERBLOCK 0x0067
+
+#define PM2_VECTOR_BASE    PROGRAM_BASE
+#define PM2_VECTOR_EXTINT0 (PM2_VECTOR_BASE + 3)
+#define PM2_VECTOR_TIMER0  (PM2_VECTOR_BASE + 11)
+#define PM2_VECTOR_EXTINT1 (PM2_VECTOR_BASE + 19)
+#define PM2_VECTOR_TIMER1  (PM2_VECTOR_BASE + 27)
+#define PM2_VECTOR_UART    (PM2_VECTOR_BASE + 35)
+#define PM2_VECTOR_TIMER2  (PM2_VECTOR_BASE + 43)
+
+/**************************************************************************
+ * Public Types
+ **************************************************************************/
+
+/**************************************************************************
+ * Public Variables
+ **************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+/* TRUE if processing an interrupt */
+
+extern boolean g_ininterrupt;
+
+#endif /* __ASSEMBLY */
+
+/**************************************************************************
+ * Public Function Prototypes
+ **************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+extern ubyte up_savecontext(FAR struct xcptcontext *context);
+extern void  up_restorecontext(FAR struct xcptcontext *context);
+
+#endif /* __ASSEMBLY */
+#endif /* __ARCH_UP_INTERNAL_H */
diff --git a/nuttx/arch/pjrc-8051/src/up_interruptcontext.c b/nuttx/arch/pjrc-8051/src/up_interruptcontext.c
new file mode 100644
index 000000000..2743ed7b0
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_interruptcontext.c
@@ -0,0 +1,68 @@
+/************************************************************
+ * up_interruptcontext.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <nuttx/arch.h>
+#include <nuttx/irq.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Private Types
+ ************************************************************/
+
+/************************************************************
+ * Private Function Prototypes
+ ************************************************************/
+
+/************************************************************
+ * Global Functions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_interrupt_context
+ *
+ * Description: Return TRUE is we are currently executing in
+ * the interrupt handler context.
+ ************************************************************/
+
+boolean up_interrupt_context(void)
+{
+   return g_ininterrupt;
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_irq.c b/nuttx/arch/pjrc-8051/src/up_irq.c
new file mode 100644
index 000000000..c524fe3e7
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_irq.c
@@ -0,0 +1,157 @@
+/************************************************************
+ * up_irq.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <nuttx/irq.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Public Data
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: irq_initialize
+ ************************************************************/
+
+void up_irqinitialize(void)
+{
+}
+
+/************************************************************
+ * Name: irqsave
+ *
+ * Description:
+ *   Disable all IRQs
+ *
+ ************************************************************/
+
+irqstate_t irqsave(void) _naked
+{
+  _asm
+	mov	ie, dpl
+	clr	ea
+	ret
+  _endasm;
+}
+
+/************************************************************
+ * Name: irqrestore
+ *
+ * Description:
+ *   Restore a previous interrupt state
+ *
+ ************************************************************/
+
+void irqrestore(irqstate_t flags) __naked
+{
+  flags; /* Avoid compiler warning about unused argument */
+  _asm
+	mov	ie, dpl
+	ret
+  _endasm;
+}
+
+/************************************************************
+ * Name: up_disable_irq
+ *
+ * Description:
+ *   Disable the IRQ specified by 'irq'
+ *
+ ************************************************************/
+
+static void _up_disable_irq(ubyte iebit) __naked
+{
+  _asm
+	mov	a, ie
+	orl	a, dpl
+	mov	ie, a
+	ret
+  _endasm;
+}
+
+void up_disable_irq(int irq)
+{
+  if ((unsigned)irq < NR_IRQS)
+    {
+       _up_disable_irq(1 << irq);
+    }
+}
+
+/************************************************************
+ * Name: up_enable_irq
+ *
+ * Description:
+ *   Enable the IRQ specified by 'irq'
+ *
+ ************************************************************/
+
+static void _up_enable_irq(ubyte iebit) __naked
+{
+  _asm
+	mov	a, ie
+	anl	a, dpl
+	mov	ie, a
+	ret
+  _endasm;
+}
+
+void up_enable_irq(int irq)
+{
+  if ((unsigned)irq < NR_IRQS)
+    {
+      _up_enable_irq(~(1 << irq));
+    }
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_putc.c b/nuttx/arch/pjrc-8051/src/up_putc.c
new file mode 100644
index 000000000..d2e486829
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_putc.c
@@ -0,0 +1,78 @@
+/************************************************************
+ * up_putc.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <nuttx/arch.h>
+#include "up_internal.h"
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+static void _up_putc(int ch) __naked
+{
+#if 0
+  ch; /* To avoid unreferenced argument warning */
+  _asm
+        mov     a, dpl
+        ljmp    PM2_ENTRY_COUT
+  _endasm;
+#else
+  ch;
+  _asm
+        mov     a, dpl
+cout:   jnb     ti, cout
+        clr     ti
+        mov     sbuf, a
+        ret
+  _endasm;
+#endif
+}
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+int up_putc(int ch)
+{
+  _up_putc(ch);
+  return ch;  
+}
+
diff --git a/nuttx/arch/pjrc-8051/src/up_releasepending.c b/nuttx/arch/pjrc-8051/src/up_releasepending.c
new file mode 100644
index 000000000..99c20ec23
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_releasepending.c
@@ -0,0 +1,134 @@
+/************************************************************
+ * up_releasepending.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Funtions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_release_pending
+ *
+ * Description:
+ *   Release and ready-to-run tasks that have
+ *   collected in the pending task list.  This can call a
+ *   context switch if a new task is placed at the head of
+ *   the ready to run list.
+ *
+ ************************************************************/
+
+void up_release_pending(void)
+{
+  FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
+
+  dbg("From TCB=%p\n", rtcb);
+
+  /* Merge the g_pendingtasks list into the g_readytorun task list */
+
+  /* sched_lock(); */
+  if (sched_mergepending())
+    {
+      /* The currently active task has changed!  We will need to
+       * switch contexts.  First check if we are operating in
+       * interrupt context:
+       */
+
+      if (g_ininterrupt)
+        {
+#if 0
+# warning REVISIT
+          /* Yes, then we have to do things differently.
+           * Just copy the current registers into the OLD rtcb.
+           */
+
+           up_copystate(&tcb->xcp, current_regs);
+
+          /* Restore the exception context of the rtcb at the (new) head 
+           * of the g_readytorun task list.
+           */
+
+          rtcb = (_TCB*)g_readytorun.head;
+          dbg("New Active Task TCB=%p\n", rtcb);
+
+          /* Then switch contexts */
+
+          up_copystate(current_regs, &tcb->xcp);
+#endif
+        }
+
+      /* Copy the exception context into the TCB of the task that
+       * was currently active. if up_savecontext returns a non-zero
+       * value, then this is really the previously running task 
+       * restarting!
+       */
+
+      else if (!up_savecontext(&rtcb->xcp))
+        {
+          /* Restore the exception context of the rtcb at the (new) head 
+           * of the g_readytorun task list.
+           */
+
+          rtcb = (FAR _TCB*)g_readytorun.head;
+          dbg("New Active Task TCB=%p\n", rtcb);
+
+           /* Then switch contexts */
+
+          up_restorecontext(&rtcb->xcp);
+        }
+    }
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_reprioritizertr.c b/nuttx/arch/pjrc-8051/src/up_reprioritizertr.c
new file mode 100644
index 000000000..dbb9db3c4
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_reprioritizertr.c
@@ -0,0 +1,181 @@
+/************************************************************
+ * up_reprioritizertr.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Funtions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_reprioritize_rtr
+ *
+ * Description:
+ *   Called when the priority of a running or
+ *   ready-to-run task changes and the reprioritization will 
+ *   cause a context switch.  Two cases:
+ *
+ *   1) The priority of the currently running task drops and the next
+ *      task in the ready to run list has priority.
+ *   2) An idle, ready to run task's priority has been raised above the
+ *      the priority of the current, running task and it now has the
+ *      priority.
+ *
+ * Inputs:
+ *   tcb: The TCB of the task that has been reprioritized
+ *   priority: The new task priority
+ *
+ ************************************************************/
+
+void up_reprioritize_rtr(FAR _TCB *tcb, ubyte priority)
+{
+  /* Verify that the caller is sane */
+
+  if (tcb->task_state < FIRST_READY_TO_RUN_STATE ||
+      tcb->task_state > LAST_READY_TO_RUN_STATE ||
+      priority < SCHED_PRIORITY_MIN || 
+      priority > SCHED_PRIORITY_MAX)
+    {
+       PANIC(OSERR_BADREPRIORITIZESTATE);
+    }
+  else
+    {
+      FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
+      boolean switch_needed;
+
+      dbg("TCB=%p PRI=%d\n", tcb, priority);
+
+      /* Remove the tcb task from the ready-to-run list.
+       * sched_removereadytorun will return TRUE if we just
+       * remove the head of the ready to run list.
+       */
+
+      switch_needed = sched_removereadytorun(tcb);
+
+      /* Setup up the new task priority */
+
+      tcb->sched_priority = (ubyte)priority;
+
+      /* Return the task to the specified blocked task list.
+       * sched_addreadytorun will return TRUE if the task was
+       * added to the new list.  We will need to perform a context
+       * switch only if the EXCLUSIVE or of the two calls is non-zero
+       * (i.e., one and only one the calls changes the head of the
+       * ready-to-run list).
+       */
+
+      switch_needed ^= sched_addreadytorun(tcb);
+
+      /* Now, perform the context switch if one is needed */
+
+      if (switch_needed)
+        {
+          /* If we are going to do a context switch, then now is the right
+           * time to add any pending tasks back into the ready-to-run list.
+           * task list now
+           */
+
+          if (g_pendingtasks.head)
+            {
+              sched_mergepending();
+            }
+
+         /* Are we in an interrupt handler? */
+
+          if (g_ininterrupt)
+            {
+#if 0
+# warning REVISIT
+              /* Yes, then we have to do things differently.
+               * Just copy the current registers into the OLD rtcb.
+               */
+
+               up_copystate(&tcb->xcp, current_regs);
+
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (_TCB*)g_readytorun.head;
+              dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_copystate(current_regs, &tcb->xcp);
+#endif
+            }
+          /* Copy the exception context into the TCB at the (old) head of the
+           * g_readytorun Task list. if up_savecontext returns a non-zero
+           * value, then this is really the previously running task restarting!
+           */
+
+          if (!up_savecontext(&rtcb->xcp))
+            {
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (FAR _TCB*)g_readytorun.head;
+              dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_restorecontext(&rtcb->xcp);
+            }
+        }
+    }
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_restorecontext.c b/nuttx/arch/pjrc-8051/src/up_restorecontext.c
new file mode 100644
index 000000000..d1d095d91
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_restorecontext.c
@@ -0,0 +1,156 @@
+/**************************************************************************
+ * up_restorecontext.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************/
+
+/**************************************************************************
+ * Included Files
+ **************************************************************************/
+
+#include <nuttx/irq.h>
+#include "up_internal.h"
+
+/**************************************************************************
+ * Private Definitions
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Types
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Function Prototypes
+ **************************************************************************/
+
+/**************************************************************************
+ * Global Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Name: up_popcontext
+ *
+ * Description:
+ *   Pop the current execution context from the stack and return to the
+ *   execution context.  Similar operations are executed from the interrupt
+ *   state restore
+ *
+ * Inputs:
+ *   None
+ *
+ * Return:
+ *   This function does not return
+ *
+ **************************************************************************/
+
+static void up_popcontext(ubyte newsp) __naked
+
+{
+  _asm 
+	pop	_bp 
+	pop	psw
+	pop	ar1 
+	pop	ar0 
+	pop	ar7 
+	pop	ar6 
+	pop	ar5 
+	pop	ar4 
+	pop	ar3 
+	pop	ar2 
+	pop	b 
+	pop	dph
+	pop	dpl 
+
+	/* Restore the interrupt state per the stored IE value */
+
+	pop	acc
+	jb	acc.7,00001$
+	clr	ie.7
+	sjmp	00002$
+  00001$:
+	setb	ie.7
+  00002$:
+
+	pop acc
+	ret
+  _endasm;
+}
+
+/**************************************************************************
+ * Public Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Name: up_restorecontext
+ *
+ * Description:
+ *   Restore the stack specified in the context structure and return to
+ *   that context
+ *
+ * Inputs:
+ *   context - Holds the stack content of the context to return to
+ *
+ * Return:
+ *   This function does not return.
+ *
+ **************************************************************************/
+
+void up_restorecontext(FAR struct xcptcontext *context)
+{
+  int nbytes = context->nbytes;
+  FAR ubyte *src = context->stack;
+  FAR ubyte *dest = (FAR ubyte*)STACK_BASE;
+
+  /* Interrupts should be disabled for the following.  up_popcontext() will
+   * set the new interrupt state correctly.
+   */
+
+  (void)irqsave();
+
+  while (nbytes--)
+    {
+      *src++ = *dest++;
+    }
+
+  /* Then return to the restored context */
+
+  up_popcontext(context->nbytes + (STACK_BASE-1));
+}
+
diff --git a/nuttx/arch/pjrc-8051/src/up_savecontext.c b/nuttx/arch/pjrc-8051/src/up_savecontext.c
new file mode 100644
index 000000000..1405fce4d
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_savecontext.c
@@ -0,0 +1,167 @@
+/**************************************************************************
+ * up_savecontext.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************/
+
+/**************************************************************************
+ * Included Files
+ **************************************************************************/
+
+#include <sys/types.h>
+#include <nuttx/irq.h>
+#include "up_internal.h"
+
+/**************************************************************************
+ * Private Definitions
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Types
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Function Prototypes
+ **************************************************************************/
+
+/**************************************************************************
+ * Global Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Name: up_pushcontext
+ *
+ * Description:
+ *   Push the current execution context onto the before the stack.  Similar
+ *   operations are executed from the interrupt state save.
+ *
+ * Inputs:
+ *   None
+ *
+ * Return:
+ *   Returns the stack pointer (always non-zero).  However, when
+ *   up_popcontext() executes, it will appear as a return from this
+ *   function with return value == 0
+ *
+ **************************************************************************/
+
+static ubyte up_pushcontext(void) __naked
+{
+  /* Push the current execution context onto the stack. */
+
+  _asm
+	push	acc
+	push	ie
+	mov	dptr, #0 /* Save return value (dpl) = 0 */
+	push	dpl
+	push	dph
+	push	b
+	push	ar2
+	push	ar3
+	push	ar4
+	push	ar5
+	push	ar6
+	push	ar7
+	push	ar0
+	push	ar1
+	push	psw
+	clr	psw
+	push	_bp
+
+	/* And return the current stack pointer value in dpl */
+
+	mov	dpl, sp
+	ret
+  _endasm;
+}
+
+/**************************************************************************
+ * Public Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Name: up_savecontext
+ *
+ * Description:
+ *   Push the current execution context onto the stack, then save the
+ *   entire stack contents in the provided context structure.
+ *
+ * Inputs:
+ *   context - the context structure in which to save the stack info
+ *
+ * Return
+ *   0 = Normal state save return
+ *   1 = This is the matching return from up_restorecontext()
+ *
+ **************************************************************************/
+
+ubyte up_savecontext(FAR struct xcptcontext *context)
+{
+  irqstate_t flags = irqsave();
+  ubyte sp = up_pushcontext();
+  if (sp)
+    {
+      /* Now copy the current stack frame (including the saved execution
+       * context) from internal RAM to XRAM.
+       */
+
+      ubyte nbytes    = sp - (STACK_BASE-1);
+      FAR ubyte *src  = (FAR ubyte*)STACK_BASE;
+      FAR ubyte *dest = context->stack;
+
+      /* Then copy the stack info into the context structure */
+
+      context->nbytes = nbytes;
+      while (nbytes--)
+        {
+          *dest++ = *src++;
+        }
+
+      /* Return zero so that the return behavior is similar to setjmp */
+
+      irqrestore(flags);
+      return 0;
+    }
+
+  /* Return one so that the return behavior is similar to setjmp */
+
+  irqrestore(flags);
+  return 1;
+}
diff --git a/nuttx/arch/pjrc-8051/src/up_unblocktask.c b/nuttx/arch/pjrc-8051/src/up_unblocktask.c
new file mode 100644
index 000000000..1c9494f36
--- /dev/null
+++ b/nuttx/arch/pjrc-8051/src/up_unblocktask.c
@@ -0,0 +1,164 @@
+/************************************************************
+ * up_unblocktask.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/************************************************************
+ * Private Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/************************************************************
+ * Private Funtions
+ ************************************************************/
+
+/************************************************************
+ * Public Funtions
+ ************************************************************/
+
+/************************************************************
+ * Name: up_unblock_task
+ *
+ * Description:
+ *   A task is currently in an inactive task list
+ *   but has been prepped to execute.  Move the TCB to the
+ *   ready-to-run list, restore its context, and start execution.
+ *
+ * Inputs:
+ *   tcb: Refers to the tcb to be unblocked.  This tcb is
+ *     in one of the waiting tasks lists.  It must be moved to
+ *     the ready-to-run list and, if it is the highest priority
+ *     ready to run taks, executed.
+ *
+ ************************************************************/
+
+void up_unblock_task(FAR _TCB *tcb)
+{
+  /* Verify that the context switch can be performed */
+
+  if ((tcb->task_state < FIRST_BLOCKED_STATE) ||
+      (tcb->task_state > LAST_BLOCKED_STATE))
+    {
+      PANIC(OSERR_BADUNBLOCKSTATE);
+    }
+  else
+    {
+      FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
+
+      dbg("Unblocking TCB=%p\n", tcb);
+
+     /* Remove the task from the blocked task list */
+
+     sched_removeblocked(tcb);
+
+     /* Reset its timeslice.  This is only meaningful for round
+      * robin tasks but it doesn't here to do it for everything
+      */
+
+#if CONFIG_RR_INTERVAL > 0
+     tcb->timeslice = CONFIG_RR_INTERVAL;
+#endif
+
+     /* Add the task in the correct location in the prioritized
+      * g_readytorun task list
+      */
+
+     if (sched_addreadytorun(tcb))
+       {
+         /* The currently active task has changed! We need to do
+          * a context switch to the new task.
+          *
+          * Are we in an interrupt handler? 
+          */
+
+          if (g_ininterrupt)
+            {
+#if 0
+# warning REVISIT
+              /* Yes, then we have to do things differently.
+               * Just copy the current registers into the OLD rtcb.
+               */
+
+               up_copystate(&tcb->xcp, current_regs);
+
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (_TCB*)g_readytorun.head;
+              dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_copystate(current_regs, &tcb->xcp);
+#endif
+            }
+
+         /* We are not in an interrupt andler.  Copy the user C context
+          * into the TCB of the task that was previously active.  if 
+          * up_savecontext returns a non-zero value, then this is really the
+          * previously running task restarting!
+          */
+
+         else if (!up_savecontext(&rtcb->xcp))
+           {
+             /* Restore the exception context of the new task that is ready to
+              * run (probably tcb).  This is the new rtcb at the head of the
+              * g_readytorun task list.
+              */
+
+             rtcb = (FAR _TCB*)g_readytorun.head;
+             dbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+             up_restorecontext(&rtcb->xcp);
+           }
+       }
+    }
+}