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https://github.com/cc65/cc65.git
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114 lines
2.3 KiB
ArmAsm
114 lines
2.3 KiB
ArmAsm
;
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; Startup code for cc65 (Vic20 version)
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;
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; This must be the *first* file on the linker command line
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;
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.export _exit
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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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.include "zeropage.inc"
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.include "vic20.inc"
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.include "../cbm/cbm.inc"
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; ------------------------------------------------------------------------
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; Create an empty LOWCODE segment to avoid linker warnings
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.segment "LOWCODE"
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; ------------------------------------------------------------------------
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; Place the startup code in a special segment.
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.segment "STARTUP"
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; BASIC header with a SYS call
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.word Head ; Load address
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Head: .word @Next
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.word 1000 ; Line number
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.byte $9E ; SYS token
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.byte <(((@Start / 1000) .mod 10) + $30)
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.byte <(((@Start / 100) .mod 10) + $30)
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.byte <(((@Start / 10) .mod 10) + $30)
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.byte <(((@Start / 1) .mod 10) + $30)
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.byte $00 ; End of BASIC line
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@Next: .word 0 ; BASIC end marker
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@Start:
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; ------------------------------------------------------------------------
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; Actual code
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ldx #zpspace-1
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L1: lda sp,x
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sta zpsave,x ; Save the zero page locations we need
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dex
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bpl L1
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; Close open files
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jsr CLRCH
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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__)
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sta sp
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lda #>(__RAM_START__ + __RAM_SIZE__)
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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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; Call module destructors. This is also the _exit entry.
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_exit: jsr donelib ; Run module destructors
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; Restore system stuff
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ldx spsave
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txs ; Restore stack pointer
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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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; Reset changed vectors, back to basic
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jmp RESTOR
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; ------------------------------------------------------------------------
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; Data
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.data
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zpsave: .res zpspace
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.bss
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spsave: .res 1
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