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mirror of https://github.com/cc65/cc65.git synced 2024-12-23 04:30:10 +00:00
cc65/libsrc/pet/crt0.s
cuz 7a5d4f3138 Fixed issues with the last change: The return code must be pulled from stack
before the stack pointer is reset.


git-svn-id: svn://svn.cc65.org/cc65/trunk@2906 b7a2c559-68d2-44c3-8de9-860c34a00d81
2004-03-08 20:38:58 +00:00

112 lines
1.9 KiB
ArmAsm

;
; Startup code for cc65 (PET version)
;
; This must be the *first* file on the linker command line
;
.export _exit
.import initlib, donelib
.import zerobss, push0
.import callmain
.import CLRCH, BSOUT
.include "zeropage.inc"
.include "pet.inc"
.include "../cbm/cbm.inc"
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
; BASIC header with a SYS call
.word Head ; Load address
Head: .word @Next
.word .version ; Line number
.byte $9E,"1037" ; SYS 1037
.byte $00 ; End of BASIC line
@Next: .word 0 ; BASIC end marker
; ------------------------------------------------------------------------
; Actual code
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x ; Save the zero page locations we need
dex
bpl L1
; Close open files
jsr CLRCH
; Switch to second charset
lda #14
; sta $E84C ; See PET FAQ
jsr BSOUT
; Clear the BSS data
jsr zerobss
; Save system stuff and setup the stack
tsx
stx spsave ; Save the system stack ptr
lda MEMSIZE
sta sp
lda MEMSIZE+1
sta sp+1 ; Set argument stack ptr
; Call module constructors
jsr initlib
; Push arguments and call main()
jsr callmain
; Call module destructors. This is also the _exit entry.
_exit: pha ; Save the return code on stack
jsr donelib ; Run module destructors
; Copy back the zero page stuff
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Store the program return code into ST
pla
sta ST
; Restore the stack pointer
ldx spsave
txs ; Restore stack pointer
; Back to basic
rts
; ------------------------------------------------------------------------
; Data
.data
zpsave: .res zpspace
.bss
spsave: .res 1
mmusave:.res 1