PS. I'm not exactly sure why the C64C bottom row is showing different "T" chars with colours compared to the Vice emulator which shows the usual "black $FF char"?
The color of that one $ff-byte on rasterline $30 is green on the emulator, but white on the real C64, is that right? If so, then there is an emulator bug.
;ZP-adresses irqA = 2 irqX = 3 irqY = 4 ;Variables IrqLijn0 = $2f IrqLijn1 = 255 *=$0801 ; 10 SYS2064 !by $0B, $08, $0A, $00, $9E, $32, $30, $36, $34, $00, $00, $00 *=$0810 ;set up stable raster interrupt and put something on screen sei lda #%100000 sta $01 ldx #0 .clm1 stx ClearMemStart inx inc .clm1+1 bne .clm1 inc .clm1+2 bne .clm1 lda #%110111 sta $01 ; Clear everything else :) ldx #0 .clm2 txa sta $0002,x sta $0102,x sta $0202,x sta $0302,x sta $0700,x sta $db00,x dex bne .clm2 cld lda #0 sta $d015 ldy #00 l0: ldx #39 tya m0: sta $0400,x m1: sta $d800,x dex bpl m0 clc lda m0+1 adc #40 sta m0+1 bcc *+5 inc m0+2 clc lda m1+1 adc #40 sta m1+1 bcc *+5 inc m1+2 iny cpy #25 bcc l0 lda #100 sta $0404 lda #1 sta $d804 lda #$7f sta $042b lda #3 sta $d82b lda #86 sta $042f lda #7 sta $d82f ldx #7 stx $dbeb ldx #5 stx $dbec ldx #13 stx $dbed jsr setTimer ;stabilize raster lda #$7f sta $dc0d sta $dd0d lda $dc0d lda $dd0d lda #$01 sta $d01a lda #IrqLijn0 sta $d012 lda #$1f sta $d011 lda #<irq0 sta $fffe lda #>irq0 sta $ffff lda #$35 sta $01 lda #$55 sta $3fff lda #$01 sta $d010 inc $d019 cli jmp * ;Raster irq every 4th line irq0: sta irqA nop lda $dc06 eor #7 sta *+4 bpl *+2 ;Note: make sure there is no page boundary crossing! lda #$a9 lda #$a9 lda $eaa5 stx irqX sty irqY ldx $d012 inc $0200 ;for delay purposes only inc $d020 ;show current line in right border dec $d020 inc $0200 ;badline on next rasterline inx txa and #$07 ora #$18 ;$38 sta $d011 txa clc adc #$03 ;irq every 4th line cmp #$f8 bcs endscrn sta $d012 inc $d019 ldy irqY ldx irqX lda irqA rti endscrn: ;open the border lda $d011 and #$f7 sta $d011 bit $d011 bpl *-3 lda #$1f ;$3f sta $d011 lda #IrqLijn0 ;IrqLijn1 sta $d012 inc $d019 ldy irqY ldx irqX lda irqA rti ;Stabilize raster setTimer: ;Via badline detection with timer lax $dc04 sbx #51 sta irqA cpx $dc04 bne setTimer ;Note: make sure there is no page boundary crossings! ;wait till cycle 54 with setting $dc0f ldx #8 dex bne *-1 bit $ea lda #8 sta $dc06 stx $dc07 lda #$11 sta $dc0f ;This instruction should happen on cycle 54 rts ClearMemStart
Emulation now matches real C64C
The bottom line does seem to be the "sprite register" area for the chars, but not the colour RAM...?!
//ZP-adresses .const irqA = 2 .const irqX = 3 .const irqY = 4 //Variables .var IrqLijn0 = $2f *=$0801 // 10 SYS2064 .byte $0B, $08, $0A, $00, $9E, $32, $30, $36, $34, $00, $00, $00 *=$0810 sei cld lda #0 sta $d015 sta $d021 lda #%10101010 sta $3fff ldy #01 l0: ldx #39 tya m0: sta $0428,x lda #$0e sta $d828,x dex bpl l0+2 clc lda m0+1 adc #40 sta m0+1 sta m0+6 bcc *+8 inc m0+2 inc m0+7 iny cpy #25 bcc l0 //Mid grey characters #123 on first character row ldx #39 l1: lda #123 sta $0400,x lda #12 sta $d800,x dex bpl l1 /Put some chars and colors in $07e8 ... $07ff and $dbe8 ... $dbff ldx #$fe l2: txa sta $0701,x sta $db01,x dex cpx #$e6 bne l2 jsr setTimer lda #$7f sta $dc0d sta $dd0d lda $dc0d lda $dd0d lda #$01 sta $d01a lda #IrqLijn0 sta $d012 lda #$1f sta $d011 lda #<irq0 sta $fffe lda #>irq0 sta $ffff lda #$35 sta $01 lda #$55 sta $3fff lda #$01 sta $d010 inc $d019 cli jmp * irq0: sta irqA nop lda $dc06 eor #7 sta *+4 bpl *+2 lda #$a9 lda #$a9 lda $eaa5 stx irqX sty irqY ldx $d012 inc $0200 inc $d020 dec $d020 inc $0200 //Badline on next rasterline inx txa and #$07 ora #$18 sta $d011 txa clc adc #$03 cmp #$f8 bcs endscrn sta $d012 inc $d019 ldy irqY ldx irqX lda irqA rti endscrn: //open border lda $d011 and #$f7 sta $d011 bit $d011 bpl *-3 lda #$1f sta $d011 lda #IrqLijn0 sta $d012 inc $d019 ldy irqY ldx irqX lda irqA rti setTimer: //Via badline detection with timer lax $dc04 sbx #51 sta irqA cpx $dc04 bne setTimer ldx #8 dex bne *-1 bit $ea lda #8 sta $dc06 stx $dc07 lda #$11 sta $dc0f rts
