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61 lines
1017 B
Plaintext
61 lines
1017 B
Plaintext
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;
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;; Commodore 64 Basic Runtime File
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;;
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;; Include this at the TOP of your C64 program, and it will handle
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;; hiding away the BASIC ROM and data and restoring it at the end.
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;;
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;; You will have a contiguous block of RAM from $0800 to $CF81, and
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;; Zero Page access from $02 to $7F in the segment "zp".
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.word $0801
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.org $0801
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; BASIC program that just calls our machine language code
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.scope
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.word _next, 10 ; Next line and current line number
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.byte $9e," 2062",0 ; SYS 2062
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_next: .word 0 ; End of program
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.scend
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.data zp ; Zero Page memory segment.
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.org $0002
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.text
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.scope
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; Cache BASIC zero page at top of available RAM
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ldx #$7E
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* lda $01, x
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sta $CF81, x
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dex
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bne -
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; Swap out the BASIC ROM for RAM
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lda $01
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and #$fe
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ora #$06
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sta $01
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; Run the real program
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jsr _main
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; Restore BASIC ROM
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lda $01
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ora #$07
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sta $01
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; Restore BASIC zero page
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ldx #$7E
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* lda $CF81, x
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sta $01, x
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dex
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bne -
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; Back to BASIC
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rts
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_main:
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; Program follows...
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.scend
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