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Commodore 1571 firmware
ROM Start

        .page
	.subttl 'romsf.src'

	*=rom   	; +$300 rom patch area
cchksm  *=*+1		; <<<<< TO BE DETERMINED

	.byte '(C)1985 COMMODORE ELECTRONICS LTD., ALL RIGHTS RESERVED'

ptch0a	and  #$ff-3
	ora  tmp
	sta  dskcnt	
ptch0b	lda  pcr2	; disable SO
	and  #$ff-2
	sta  pcr2
	rts

	  ; track cutoffs	
trackn  .byte 41,31,25,18
	
worktable ; table of track densities extras for those who address tracks > 35
	.byte $60,$60,$60,$60,$60,$60,$60,$60,$60,$60
	.byte $60,$60,$60,$60,$60,$60,$60
	.byte $40,$40,$40,$40,$40,$40,$40
	.byte $20,$20,$20,$20,$20,$20
	.byte $00,$00,$00,$00,$00
	.byte $00,$00,$00,$00,$00,$00

ptch0c	sta cmd		; save off cmd for DOS
	pha
	lda #1		; trk one
	sta hdrs,x
	pla
	rts		; return

ptch0d  sei		; no irq's
	lda  pcr2
	ora  #$0e
	sta  pcr2	; enable SO
	jsr  jclear	; clear track (val in .x)
	jsr  kill	; disable write
	lda  pcr2
	and  #$ff-$0e
	sta  pcr2	; disable SO
	cli
	rts

	
*=rom+256        	; c0 patch space


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This page has been created by Sami Rautiainen.
Read the small print. Last updated August 27, 1998.