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cc65/libsrc/atmos/crt0.s

114 lines
2.9 KiB
ArmAsm

;
; Startup code for cc65 (Oric version)
;
; By Debrune Jérôme <jede@oric.org> and Ullrich von Bassewitz <uz@cc65.org>
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import callmain, zerobss
.import __RAM_START__, __RAM_SIZE__
.import __ZPSAVE_LOAD__, __STACKSIZE__
.include "zeropage.inc"
.include "atmos.inc"
; ------------------------------------------------------------------------
; Oric tape header
.segment "TAPEHDR"
.byte $16, $16, $16 ; Sync bytes
.byte $24 ; End of header marker
.byte $00 ; $2B0
.byte $00 ; $2AF
.byte $80 ; $2AE Machine code flag
.byte $C7 ; $2AD Autoload flag
.dbyt __ZPSAVE_LOAD__ - 1 ; $2AB
.dbyt __RAM_START__ ; $2A9
.byte $00 ; $2A8
.byte ((.VERSION >> 8) & $0F) + '0'
.byte ((.VERSION >> 4) & $0F) + '0'
.byte (.VERSION & $0F) + '0'
.byte $00 ; Zero terminated compiler version
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
; Save the zero page area we're about to use
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x ; Save the zero page locations we need
dex
bpl L1
; Clear the BSS data
jsr zerobss
; Unprotect columns 0 and 1
lda STATUS
sta stsave
and #%11011111
sta STATUS
; Save system stuff and setup the stack
tsx
stx spsave ; Save system stk ptr
lda #<(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
sta sp
lda #>(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
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: jsr donelib ; Run module destructors
; Restore system stuff
ldx spsave
txs
lda stsave
sta STATUS
; Copy back the zero page stuff
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Back to BASIC
rts
; ------------------------------------------------------------------------
.segment "ZPSAVE"
zpsave: .res zpspace
; ------------------------------------------------------------------------
.bss
spsave: .res 1
stsave: .res 1