;**************************************************************************
; arch/z80/src/z180/z180_head.asm
;
; Copyright (C) 2012 Gregory Nutt. All rights reserved.
; Author: Gregory Nutt <gnutt@nuttx.org>
;
; 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 NuttX 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.
;
;**************************************************************************
.title NuttX for the Z180
.module z180_head
;**************************************************************************
; Constants
;**************************************************************************
; Default stack base (needs to be fixed)
.include "asm_mem.h"
;**************************************************************************
; Global symbols used
;**************************************************************************
.globl _os_start ; OS entry point
.globl _up_vectcommon ; Common interrupt handling logic
.globl _z180_mmu_lowinit ; MMU initialization logic
.globl s__HEAP ; Start of the heap
;**************************************************************************
; Reset entry point
;**************************************************************************
.area _HEADER (ABS)
.org 0x0000
di ; Disable interrupts
im 1 ; Set interrupt mode 1
jr _up_reset ; And boot the system
;**************************************************************************
; Other reset handlers
;**************************************************************************
.org 0x0008 ; RST 1
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #0 ; 0 = Z180_RST1
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0010 ; RST 2
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #1 ; 1 = Z180_RST2
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0018 ; RST 3
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #2 ; 2 = Z180_RST3
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0020 ; RST 4
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #3 ; 3 = Z180_RST4
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0028 ; RST 5
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #4 ; 4 = Z180_RST5
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0030 ; RST 6
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #5 ; 5 = Z180_RST6
jp _up_vectcommon ; Remaining RST handling is common
.org 0x0038 ; Int mode 1 / RST 7
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #6 ; 6 = Z180_RST7
jp _up_vectcommon ; Remaining RST handling is common
;**************************************************************************
; NMI interrupt handler
;**************************************************************************
.org 0x0066
retn
;**************************************************************************
; System start logic
;**************************************************************************
_up_reset:
; Set up the stack pointer at the location determined the Makefile
; and stored in asm_mem.h
ld SP, #CONFIG_STACK_END ; Set stack pointer
; Configure the MMU so that things will lie at the addresses that we
; expect them to
call _z180_mmu_lowinit ; Initialize the MMU
; Performed initialization unique to the SDCC toolchain
call gsinit ; Initialize the data section
; Then start NuttX
call _os_start ; jump to the OS entry point
; NuttX will never return, but just in case...
_up_halt::
halt ; We should never get here
jp _up_halt
;**************************************************************************
; Ordering of segments for the linker (SDCC only)
;**************************************************************************
.area _HOME
.area _CODE
.area _INITIALIZER
.area _GSINIT
.area _GSFINAL
.area _DATA
.area _INITIALIZED
.area _BSEG
.area _BSS
.area _HEAP
;**************************************************************************
; Global data initialization logic (SDCC only)
;**************************************************************************
.area _GSINIT
gsinit::
ld bc, #l__INITIALIZER
ld a, b
or a, c
jr Z, gsinit_next
ld de, #s__INITIALIZED
ld hl, #s__INITIALIZER
ldir
gsinit_next:
.area _GSFINAL
ret
;**************************************************************************
; The start of the heap (SDCC only). Note that is actually resides in
; the _CODE area (which may be FLASH or ROM)
;**************************************************************************
.area _CODE
_g_heapbase::
.dw #s__HEAP
