243 lines
5.7 KiB
ArmAsm
243 lines
5.7 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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;---------------------------------------------------------------------
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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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