nesasm

    ;reset controller port 1 (address $4016) by storing #$1000
    ;remember that loads and stores are done one byte at a time
    lda #$10
    sta $4016
    lda #$00
    sta $4016
    ;read button states, in order
    ;A, B, Start, Select, Up, Down, Left, Right
    ;jump to corresponding subroutine if button is pressed
    lda $4016
    and #1
    beq @ASkp
    jsr Pad1_A
    @ASkp:
    lda $4016
    and #1
    bne BSkp
    lda $4016
    and #1
    bne StartSkp
    lda $4016
    and #1
    bne SelectSkp
    lda $4016
    and #1
    bne UpSkp
    lda $4016
    and #1
    bne DownSkp
    lda $4016
    and #1
    bne LeftSkp
    lda $4016
    and #1
    bne RightSkp