[Coco] Speech Systems Stereo Pak

[RETRO Innovations]

On 10/17/2020 8:50 PM, Bill Pierce via Coco wrote:
> Tim, I looked through my notes and what I have on the SS Stereo Pak was what I found in Lester's sources for Lyra's "TV Play" and Musica's SSPak options. Basically the code was the same in each one.
> There is a "setup" routine to set the unit to "ready for data", that is done once, before interrupts are blocked and sound loop starts
>
> * Set up Speech Systems Stereo Paksspkon clr >$FF71 clr >$FF73 lda #$FF sta >$FF70 sta >$FF72 lda #$04 sta >$FF71 sta >$FF73
>          rts

This makes sense if the Stereo Pak uses a MC6821 as the means to store 
and output the 8 bit values.

BASE = $ff70

PORTA = BASE

DDRA = BASE

CTRLA = BASE +1

PORTB = BASE + 2

DDRB = BASE + 2

CTRLB = BASE + 3

DDR_ACCESS = $04 ; 0 = DDR, 1 = PORT


clr CTRLA ; select DDR in PORT/DDR select

clr CTRLB ; select DDR in PORT/DDR select

lda #$ff

sta DDRA

sta DDRB

lda #DDR_ACCESS

sta CTLRA

sta CTLRB

*To be safe, I'd probably zero out the PORTS as well:*

clr PORTA

clr PORTB

; now, start sending data...

Jim