mirror of
https://github.com/irmen/prog8.git
synced 2024-12-26 14:29:35 +00:00
168 lines
3.1 KiB
NASM
168 lines
3.1 KiB
NASM
;
|
|
; This program plays a short mono 16 bit PCM sample on repeat
|
|
; It uses the AFLOW IRQ that signals when the Fifo is about to drain empty.
|
|
; The flashing green bar is when the routine is busy copying sample data into the fifo.
|
|
;
|
|
; source code is for 64TASS, assemble with: 64tass pcmplay2.asm -o pcmplay2.prg
|
|
;
|
|
|
|
.cpu 'w65c02'
|
|
.enc 'none'
|
|
|
|
* = $0801
|
|
; basic launcher
|
|
.word $080b, 2022
|
|
.text $9e, "2061", $00
|
|
.word 0
|
|
entrypoint:
|
|
|
|
|
|
CHROUT = $ffd2
|
|
VERA_ADDR_L = $9f20
|
|
VERA_ADDR_M = $9f21
|
|
VERA_ADDR_H = $9f22
|
|
VERA_DATA0 = $9f23
|
|
VERA_CTRL = $9f25
|
|
VERA_IEN = $9f26
|
|
VERA_ISR = $9f27
|
|
VERA_AUDIO_CTRL = $9f3b
|
|
VERA_AUDIO_RATE = $9f3c
|
|
VERA_AUDIO_DATA = $9f3d
|
|
IRQ_VECTOR = $0314
|
|
r0 = $02
|
|
r0L = $02
|
|
r0H = $03
|
|
r1 = $04
|
|
r1L = $04
|
|
r1H = $05
|
|
pcm_ptr = $06
|
|
|
|
|
|
; stop playback and select mono 16 bit, max volume
|
|
stz VERA_AUDIO_RATE
|
|
lda #%10101111
|
|
sta VERA_AUDIO_CTRL
|
|
|
|
; fill the fifo with some silence
|
|
ldy #1024/256
|
|
_z1: ldx #0
|
|
_z2: stz VERA_AUDIO_DATA
|
|
dex
|
|
bne _z2
|
|
dey
|
|
bne _z1
|
|
|
|
ldx #<audio_on_txt
|
|
ldy #>audio_on_txt
|
|
jsr print
|
|
|
|
ldx #<pcm_data
|
|
ldy #>pcm_data
|
|
stx pcm_ptr
|
|
sty pcm_ptr+1
|
|
|
|
; set interrupt handler
|
|
sei
|
|
ldx #<irq_handler
|
|
ldy #>irq_handler
|
|
stx IRQ_VECTOR
|
|
sty IRQ_VECTOR+1
|
|
lda #%00001000 ; enable the AFLOW irq
|
|
sta VERA_IEN
|
|
cli
|
|
|
|
lda #21
|
|
sta VERA_AUDIO_RATE ; start playback
|
|
|
|
_wait:
|
|
wai
|
|
bra _wait
|
|
|
|
|
|
irq_handler:
|
|
lda VERA_ISR
|
|
and #%00001000 ; is aflow?
|
|
bne _aflow_irq
|
|
; handle other irq here
|
|
bra _exit_irq
|
|
|
|
_aflow_irq:
|
|
; paint a screen color
|
|
stz VERA_CTRL
|
|
lda #$0c
|
|
sta VERA_ADDR_L
|
|
lda #$fa
|
|
sta VERA_ADDR_M
|
|
lda #$01
|
|
sta VERA_ADDR_H
|
|
lda #$a0
|
|
sta VERA_DATA0
|
|
|
|
; refill fifo buffer (minimum 1Kb = 1/4)
|
|
; this assumes all samples are aligned to page size!
|
|
; so we can at least copy a full page at once here.
|
|
ldx #8 ; number of pages to copy
|
|
_copy_more_pages:
|
|
ldy #0
|
|
_c1: lda (pcm_ptr),y
|
|
sta VERA_AUDIO_DATA ; lsb
|
|
iny
|
|
lda (pcm_ptr),y
|
|
sta VERA_AUDIO_DATA ; msb
|
|
iny
|
|
; (in case of 16 bit stereo output, this can be unrolled by 2 bytes again).
|
|
bne _c1
|
|
inc pcm_ptr+1
|
|
|
|
; have we reached the end of the sample data? (pcm_ptr >= pcm_data_end)
|
|
; due to page size alignment only the MSB has to be checked
|
|
lda pcm_ptr+1
|
|
cmp #>pcm_data_end
|
|
bcc _not_at_end
|
|
bne _end_reached
|
|
; lda pcm_ptr ; uncomment if lsb also needs to be checked
|
|
; cmp #<pcm_data_end
|
|
; bcs _end_reached
|
|
|
|
_not_at_end:
|
|
; note: filling the fifo until the Fifo Full bit is set doesn't seem to work reliably
|
|
; so we just fill it with a fixed number of samples.
|
|
; in this case 8 pages = 2Kb which fills the fifo back up to 50%-75%.
|
|
dex
|
|
bne _copy_more_pages
|
|
|
|
lda #$00
|
|
sta VERA_DATA0 ; back to other screen color
|
|
|
|
_exit_irq:
|
|
ply
|
|
plx
|
|
pla
|
|
rti
|
|
|
|
_end_reached:
|
|
lda #<pcm_data
|
|
sta pcm_ptr
|
|
lda #>pcm_data
|
|
sta pcm_ptr+1
|
|
bra _not_at_end
|
|
|
|
|
|
audio_on_txt: .text "AUDIO ON (IRQ)", $0d, $00
|
|
|
|
print: ; -- print string pointed to by X/Y
|
|
stx r0L
|
|
sty r0H
|
|
ldy #0
|
|
_chr: lda (r0),y
|
|
beq _done
|
|
jsr $ffd2
|
|
iny
|
|
bne _chr
|
|
_done: rts
|
|
|
|
.align $0100
|
|
pcm_data:
|
|
.binary "small-pcm-mono.bin"
|
|
pcm_data_end:
|