1c77f6f1d5
- The cc65 assembler variable 'sp' (the pointer to the C stack) is actually part of the cc65 zero page area so there's no need to manage it explicitly. Furthermore it is known to reside at the very start of the area so it can be initialized there for new threads.
245 lines
5.8 KiB
ArmAsm
245 lines
5.8 KiB
ArmAsm
;
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; Copyright (c) 2004, Adam Dunkels.
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; All rights reserved.
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;
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; Redistribution and use in source and binary forms, with or without
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; modification, are permitted provided that the following conditions
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; are met:
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; 1. Redistributions of source code must retain the above copyright
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; notice, this list of conditions and the following disclaimer.
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; 2. Redistributions in binary form must reproduce the above copyright
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; notice, this list of conditions and the following disclaimer in the
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; documentation and/or other materials provided with the distribution.
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; 3. Neither the name of the Institute nor the names of its contributors
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; may be used to endorse or promote products derived from this software
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; without specific prior written permission.
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;
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; THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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; ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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; IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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; ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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; FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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; OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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; HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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; LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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; OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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; SUCH DAMAGE.
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;
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; This file is part of the Contiki operating system.
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;
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; Author: Adam Dunkels <adam@sics.se>
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;
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; $Id: mtarch-asm.S,v 1.2 2007/08/10 10:45:35 oliverschmidt Exp $
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;
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;---------------------------------------------------------------------
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.import __ZP_START__
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.import _mtarch_asm_threadspreg
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.import _mtarch_asm_threadzp
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.import _mtarch_asm_threadstack
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.export _mtarch_asm_start
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.export _mtarch_asm_yield
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.export _mtarch_asm_exec
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;---------------------------------------------------------------------
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.bss
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kernelspreg: .res 1
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zpsave: .res 2
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zpspace = 26 ; see <cc65 source>/asminc/zeropage.inc
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;---------------------------------------------------------------------
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.code
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; Switch to thread defined by threadzp, threadstack and threadspreg.
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; The kernel CPU stack is swapped onto the threadstack, and the
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; CPU stack pointer is saved to the local variable "kernelspreg".
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; Also, the zeropage variables are saved.
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_mtarch_asm_exec:
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sei
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; Save kernel CPU stack pointer
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tsx
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stx kernelspreg
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; Save zp locations FE/FF
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lda $FE
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sta zpsave
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lda $FF
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sta zpsave+1
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; Get zero page buffer addr
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lda _mtarch_asm_threadzp
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sta $FE
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lda _mtarch_asm_threadzp+1
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sta $FF
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; Swap zero page content with buffer content
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ldy #0
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: lda <__ZP_START__,y
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tax
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lda ($FE),y
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sta <__ZP_START__,y
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txa
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sta ($FE),y
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iny
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cpy #zpspace
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bne :-
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; Get CPU stack buffer addr
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lda _mtarch_asm_threadstack
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sta $FE
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lda _mtarch_asm_threadstack+1
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sta $FF
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; Get CPU stack size
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ldy kernelspreg ; Determine the smallest of the two stack pointers,
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cpy _mtarch_asm_threadspreg ; as we only need to swap the used part of the stack.
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bcc :+
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ldy _mtarch_asm_threadspreg
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; Swap CPU stack content with buffer content
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: lda $0100,y
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tax
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lda ($FE),y
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sta $0100,y
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txa
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sta ($FE),y
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iny
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bne :-
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; Restore zp locations FE/FF
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lda zpsave
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sta $FE
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lda zpsave+1
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sta $FF
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; Set thread CPU stack pointer
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ldx _mtarch_asm_threadspreg
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txs
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pla
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tay
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pla
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tax
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pla
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rti
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;---------------------------------------------------------------------
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; Switch from thread defined by threadzp, threadstack and threadspreg.
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; The kernel CPU stack is swapped back from the threadstack, and the
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; CPU stack pointer is restored from the local variable "kernelspreg".
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; Also, the zeropage variables are restored.
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_mtarch_asm_yield:
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php
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pha
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txa
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pha
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tya
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pha
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sei
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tsx ; The rts adds 1 to the PC
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; saved on the stack. We want
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lda $0105,x ; the stack to look like is would
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clc ; do inside of an interrupt
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adc #1 ; (this is what the 'rts' does,
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sta $0105,x ; but not the 'rti').
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lda $0106,x
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adc #0
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sta $0106,x
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; Save thread CPU stack pointer
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tsx
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stx _mtarch_asm_threadspreg
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; Save zp locations FE/FF
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lda $FE
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sta zpsave
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lda $FF
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sta zpsave+1
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; Get zero page buffer addr
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lda _mtarch_asm_threadzp
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sta $FE
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lda _mtarch_asm_threadzp+1
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sta $FF
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; Swap zero page content with buffer content
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ldy #0
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: lda <__ZP_START__,y
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tax
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lda ($FE),y
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sta <__ZP_START__,y
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txa
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sta ($FE),y
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iny
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cpy #zpspace
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bne :-
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; Get CPU stack buffer addr
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lda _mtarch_asm_threadstack
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sta $FE
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lda _mtarch_asm_threadstack+1
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sta $FF
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; Get CPU stack size
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ldy kernelspreg ; Determine the smallest of the two stack pointers,
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cpy _mtarch_asm_threadspreg ; as we only need to swap the used part of the stack.
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bcc :+
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ldy _mtarch_asm_threadspreg
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; Swap CPU stack content with buffer content
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: lda $0100,y
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tax
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lda ($FE),y
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sta $0100,y
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txa
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sta ($FE),y
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iny
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bne :-
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; Restore zp locations FE/FF
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lda zpsave
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sta $FE
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lda zpsave+1
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sta $FF
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; Set kernel CPU stack pointer
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ldx kernelspreg
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txs
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cli
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rts
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;---------------------------------------------------------------------
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_mtarch_asm_start:
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; Save zp locations FE/FF
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lda $FE
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sta zpsave
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lda $FF
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sta zpsave+1
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; Get zero page buffer addr
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lda _mtarch_asm_threadzp
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sta $FE
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lda _mtarch_asm_threadzp+1
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sta $FF
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; Copy zero page content to buffer
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ldy #$00
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: lda <__ZP_START__,y
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sta ($FE),y
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iny
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cpy #zpspace
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bne :-
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; Restore zp locations FE/FF
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lda zpsave
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sta $FE
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lda zpsave+1
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sta $FF
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rts
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;---------------------------------------------------------------------
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