nes-proj/cpu/6502/mtarch-asm.S

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;
; Copyright (c) 2004, Adam Dunkels.
; All rights reserved.
;
; 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 of the Institute 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 INSTITUTE 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 INSTITUTE 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 is part of the Contiki operating system.
;
; Author: Adam Dunkels <adam@sics.se>
;
; $Id: mtarch-asm.S,v 1.1 2007/04/21 22:15:45 oliverschmidt Exp $
;
;---------------------------------------------------------------------
.importzp ptr1
.importzp sp
.import __ZP_START__
.import _mtarch_asm_threadspreg
.import _mtarch_asm_threadsp
.import _mtarch_asm_threadzp
.import _mtarch_asm_threadstack
.export _mtarch_asm_start
.export _mtarch_asm_yield
.export _mtarch_asm_exec
;---------------------------------------------------------------------
.bss
kernelsp: .res 2
kernelspreg: .res 1
zpsize = 32
;---------------------------------------------------------------------
.code
; Switch to thread defined by threadsp, threadstack and threadspreg.
; The kernel stack is swapped onto the threadstack, and the
; sp and spreg are saved to the local variables "kernelsp" and
; "kernelspreg". Also, the zeropage variables are saved.
_mtarch_asm_exec:
sei
; Save current stack pointer
lda sp
sta kernelsp
lda sp+1
sta kernelsp+1
tsx
stx kernelspreg
lda _mtarch_asm_threadzp
sta ptr1
lda _mtarch_asm_threadzp+1
sta ptr1+1
ldy #0
: lda <__ZP_START__,y
tax
lda (ptr1),y
sta <__ZP_START__,y
txa
sta (ptr1),y
iny
cpy #zpsize
bne :-
lda _mtarch_asm_threadstack
sta ptr1
lda _mtarch_asm_threadstack+1
sta ptr1+1
ldy kernelspreg ; Determine the smallest of the two stack pointers,
cpy _mtarch_asm_threadspreg ; as we only need to swap the used part of the stack.
bcc :+
ldy _mtarch_asm_threadspreg
: lda $0100,y
tax
lda (ptr1),y
sta $0100,y
txa
sta (ptr1),y
iny
bne :-
lda _mtarch_asm_threadsp
sta sp
lda _mtarch_asm_threadsp+1
sta sp+1
ldx _mtarch_asm_threadspreg
txs
pla
tay
pla
tax
pla
rti
;---------------------------------------------------------------------
; Switch from thread defined by threadsp, threadstack and threadspreg.
; The kernel stack is swapped back from the threadstack, and the
; sp and spreg are restored from the local variables "kernelsp" and
; "kernelspreg".
_mtarch_asm_yield:
php
pha
txa
pha
tya
pha
sei
tsx ; The rts adds 1 to the PC
; saved on the stack. We want
lda $0105,x ; the stack to look like is would
clc ; do inside of an interrupt
adc #1 ; (this is what the 'rts' does,
sta $0105,x ; but not the 'rti').
lda $0106,x
adc #0
sta $0106,x
lda sp
sta _mtarch_asm_threadsp
lda sp+1
sta _mtarch_asm_threadsp+1
tsx
stx _mtarch_asm_threadspreg
lda _mtarch_asm_threadzp
sta ptr1
lda _mtarch_asm_threadzp+1
sta ptr1+1
ldy kernelspreg ; Determine the smallest of the two stack pointers,
cpy _mtarch_asm_threadspreg ; as we only need to swap the used part of the stack.
bcc :+
ldy _mtarch_asm_threadspreg
: lda <__ZP_START__,y
tax
lda (ptr1),y
sta <__ZP_START__,y
txa
sta (ptr1),y
iny
cpy #zpsize
bne :-
lda _mtarch_asm_threadstack
sta ptr1
lda _mtarch_asm_threadstack+1
sta ptr1+1
ldy #0
: lda $0100,y
tax
lda (ptr1),y
sta $0100,y
txa
sta (ptr1),y
iny
bne :-
lda kernelsp
sta sp
lda kernelsp+1
sta sp+1
ldx kernelspreg
txs
cli
rts
;---------------------------------------------------------------------
_mtarch_asm_start:
lda _mtarch_asm_threadzp
sta ptr1
lda _mtarch_asm_threadzp+1
sta ptr1+1
ldy #0
: lda <__ZP_START__,y
sta (ptr1),y
iny
cpy #zpsize
bne :-
rts
;---------------------------------------------------------------------