Custom Characters

; Adapted from a posted Lemon64 Example
; Works best if program is placed at $1000

; *********************************
; *** Character Change Routines ***
; *********************************

changechar
    ; Turn off Keyscan Interrupt
    lda $dc0e
    and #$fe
    sta $dc0e

    ;Make ROM Visible
    lda $01
    and #$fb
    sta $01

charchangeloop
charfrom
    lda $d800   ;$d800/55295 low/gr
                ;$d000/53248 upp/gr
charto
    sta $3800   ;14336

    lda charfrom+2
    sta $040a
    lda charfrom+1
    sta $040b
    lda charto+2
    sta $0432
    lda charto+1
    sta $0433

    ldx charto+1
    cpx #$f8
    bne scharcheckend

charcheckend
    lda charto+2
    cmp #$3f
    beq charchangeend

scharcheckend
    cpx #$ff
    beq charroll
    inx
    stx charto+1
    inc charfrom+1
    jmp charchangeloop

charroll
    ldx #$00
    stx charfrom+1
    stx charto+1
    ldx charfrom+2
    inx
    stx charfrom+2
    ldx charto+2
    inx
    stx charto+2
    jmp charchangeloop

charchangeend

    ; Important! for Keyset Set ROM hidden again.
    lda $01
    ora #$04
    sta $01

    ;Keyscan interrupt back on
    lda $dc0e
    ora #$01
    sta $dc0e

    ;Switch charset pointer to here
    ;$3000 is set by last 3 buts to %110
    ;12288 - 14335
    lda #%00011110
    sta $d018

    ;Put Custom Chars in Memory
    ldx #$00
charb
    lda roadchar,x
    sta $3810,x ; 3808=a, 3810=b
    inx
    cpx #$08
    bne charb


roadchar
!byte %00000000
!byte %11111111
!byte %10000001
!byte %10000001
!byte %10000001
!byte %10000001
!byte %10000001
!byte %11111111
!byte $00