CheckSlot:
    ld     hl,$0000        ; look at ROM from $0000
    ld     bc,$003c        ; loop 256 times, mask $3c
    ld     a,(hl)          ; get byte
    and    c               ; and with $3c = %00111100
    ld     e,a             ; store in e

 Loop:
    ld     a,(hl)          ; get byte
    inc    l               ; pointer++
    and    c               ; and with $3c
    cp     e               ; compare to first byte
    jp     nz,$0000        ; if not equal, run slot
    djnz   Loop            ; repeat 256 times
    ret                    ; Nothing found