checkforkeys

        ldx #5            ;number of keys-1 to check
checkkeyloop
        lda keycolumn,x
        sta $dc00
        lda $dc01
        eor #$ff
        ldy keyindex,x
        and keyrow,x
        sta $00,y

        dex
        bpl checkkeyloop

keycolumn ;6 bytes
        .byte $7f,$fd,$bf,$7f,$bf,$df    ;runstop,lshift,/,space,poundkey,p
keyrow    ;6 bytes
        .byte $80,$80,$80,$10,$01,$02
keyindex  ;6 bytes
        .byte <exitkey,<leftflipper,<rightflipper,<tiltkey,<crsrdown,<pausekey