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+xtrs README
+^^^^^^^^^^^^^
+
+TRS80 Model 3.  This port uses a vintage computer based on the Z80.
+An emulator for this computer is available to run TRS80 programs on a 
+linux platform (http://www.tim-mann.org/xtrs.html).
+
+The SDCC toolchain is available from http://sdcc.sourceforge.net/.  All
+testing has been performed using version 2.6.0 of the SDCC toolchain.
+
+Configuring NuttX
+^^^^^^^^^^^^^^^^^
+
+  ostest
+    This configuration performs a simple, minimal OS test using
+    examples/ostest.  This can be configurated as follows:
+
+	cd tools
+	./configure.sh xtrs/ostest
+	cd -
+	. ./setenv.sh
+
+
+  nsh
+    This configuration file builds NSH (examples/nsh).  This
+    configuration is not functional due to issues with use of the
+    simulated serial driver (see the TODO list).
+
+    This configuration can be selected by:
+
+	cd tools
+	./configure.sh xtrs/nsh
+	cd -
+	. ./setenv.sh
+
+ pashello
+    Configures to use examples/pashello for execution from FLASH
+    See examples/README.txt for information about pashello.
+
+    This configuration is not usable because the resulting binary
+    is too large for the z80 address space.
+
+    This configuration can be selected by:
+
+	cd tools
+	./configure.sh xtrs/pashello
+	cd -
+	. ./setenv.sh
+
+Building the SDCC toolchain
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The SDCC toolchain is built with the standard configure/make/make install
+sequence.  However, some special actions are required to generate libraries
+compatible with this build.  First start with the usual steps
+
+  download
+  unpack
+  cd sdcc
+  ./configure
+
+But before making, we need to apply a patch to the SDCC 2.6.0 source
+so that the z80 assembler can handle long symbol names
+
+  Apply sdcc-2.6.0-asz80-symlen.patch
+  cd sdcc/device/lib
+
+Then make the SDCC binaries
+
+  cd sdcc
+  make
+
+and install SDCC:
+
+  sudo make install