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98 lines
1.5 KiB
ArmAsm
98 lines
1.5 KiB
ArmAsm
;
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; Startup code for cc65 (Vic20 version)
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;
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.export _exit
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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import initlib, donelib
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.import zerobss, push0
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.import callmain
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.import RESTOR, BSOUT, CLRCH
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.import __RAM_START__, __RAM_SIZE__ ; Linker generated
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.import __STACKSIZE__ ; Linker generated
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.importzp ST
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.include "zeropage.inc"
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.include "vic20.inc"
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; ------------------------------------------------------------------------
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; Startup code
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.segment "STARTUP"
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Start:
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; Save the zero page locations we need
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ldx #zpspace-1
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L1: lda sp,x
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sta zpsave,x
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dex
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bpl L1
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; Switch to second charset
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lda #14
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jsr BSOUT
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; Clear the BSS data
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jsr zerobss
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; Save system stuff and setup the stack
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tsx
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stx spsave ; Save the system stack ptr
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lda #<(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
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sta sp
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lda #>(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
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sta sp+1 ; Set argument stack ptr
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; Call module constructors
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jsr initlib
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; Push arguments and call main()
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jsr callmain
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; Back from main (This is also the _exit entry). Run module destructors
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_exit: pha ; Save the return code on stack
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jsr donelib
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; Copy back the zero page stuff
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ldx #zpspace-1
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L2: lda zpsave,x
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sta sp,x
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dex
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bpl L2
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; Place the program return code into ST
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pla
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sta ST
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; Restore the stack pointer
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ldx spsave
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txs
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; Back to basic
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rts
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; ------------------------------------------------------------------------
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.segment "ZPSAVE"
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zpsave: .res zpspace
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; ------------------------------------------------------------------------
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.bss
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spsave: .res 1
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