.inesprg 1 ;1x 16kb PRG code
    .ineschr 0 ;0x 8kb CHR data
    .inesmap 0 ; mapper 0 = NROM, no bank swapping
    .inesmir 1 ;background mirroring (vertical mirroring = horizontal scrolling)


;----- first 8k bank of PRG-ROM   
    .bank 0
    .org $C000
   
irq:
nmi:
    rti

reset:
    sei
    cld
    lda #%00000001
    sta $4015 ;enable Square 1
   
    lda #%10001111 ; duty 10, env on+NO loop, period $0F
    sta $4000

    lda #$dc    ;tone freq
    sta $4002   ;low 8 bits of period
    lda #$02
    sta $4003   ;high 3 bits of period


forever:
    jmp forever


   
;----- second 8k bank of PRG-ROM   
    .bank 1
    .org $E000
;---- vectors
    .org $FFFA     ;first of the three vectors starts here
    .dw nmi        ;when an NMI happens (once per frame if enabled) the processor will jump to the label NMI:
    .dw reset      ;when the processor first turns on or is reset, it will jump to the label reset:
    .dw irq        ;external interrupt IRQ is not used in this tutorial