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