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cc65/libsrc/gamate/crt0.s

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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import initlib, donelib, callmain
.import push0, _main, zerobss, copydata
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.import IRQStub
; Linker generated symbols
.import __RAM_START__, __RAM_SIZE__
.import __ROM_START__, __ROM_SIZE__
.import __STARTUP_LOAD__,__STARTUP_RUN__, __STARTUP_SIZE__
.import __CODE_LOAD__,__CODE_RUN__, __CODE_SIZE__
.import __RODATA_LOAD__,__RODATA_RUN__, __RODATA_SIZE__
.include "zeropage.inc"
.include "gamate.inc"
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.segment "STARTUP"
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.word 0 ; +00 checksum from 7000-7fff (simple 8bit adds)
.byte 1, 0, 1 ; +02 flags
.byte "COPYRIGHT BIT CORPORATION", 0, $ff ; +05 copyright
; system vectors
jmp reset ; +20 reset entry
jmp nmi ; +23 nmi entry
jmp IRQStub ; +26 irq entry (135 hz)
;-------------------------------------------------------------------------------
reset:
; setup the CPU and System-IRQ
; Initialize CPU
sei
cld
; Setup stack and memory mapping
ldx #$FF ; Stack top ($01FF)
txs
; Clear the BSS data
jsr zerobss
; Copy the .data segment to RAM
jsr copydata
; setup the stack
lda #<(__RAM_START__+__RAM_SIZE__)
sta sp
lda #>(__RAM_START__+__RAM_SIZE__)
sta sp + 1
; Call module constructors
jsr initlib
cli ; allow IRQ only after constructors have run
; Pass an empty command line
jsr push0 ; argc
jsr push0 ; argv
ldy #4 ; Argument size
jsr _main ; call the users code
; Call module destructors. This is also the _exit entry.
_exit:
jsr donelib ; Run module destructors
; reset (start over)
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jmp reset
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.export initmainargs
initmainargs:
rts
;-------------------------------------------------------------------------------
nmi:
rts