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https://github.com/cc65/cc65.git
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127 lines
2.5 KiB
ArmAsm
127 lines
2.5 KiB
ArmAsm
;
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; Startup code for cc65 (C64 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 _main
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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 "c64.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,"2061" ; SYS 2061
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.byte $00 ; End of BASIC line
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@Next: .word 0 ; BASIC end marker
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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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; Switch off the BASIC ROM
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lda $01
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pha ; Remember the value
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and #$F8
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ora #$06 ; Enable kernal+I/O, disable basic
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sta $01
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; Clear the BSS data
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jsr zerobss
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; Save system settings and setup the stack
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pla
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sta mmusave ; Save the memory configuration
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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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; Pass an empty command line
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jsr push0 ; argc
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jsr push0 ; argv
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ldy #4 ; Argument size
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jsr _main ; call the users code
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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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lda mmusave
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sta $01 ; Restore memory configuration
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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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mmusave:.res 1
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