A little help with programming...

> > Hi guys,
> > I'm very sorry to bother you all, but I was wondering if there was
> > someone who might be able to donate a small amount of time to help me
> > with a particular programming issue that I am having.
>
> Could you be more specific?

Certainly. But to begin with - I have to point out that I am not a
programmer, so please be gentle!

I'm trying to write data to the AY38912 via the two controller ports.
I guess there a few ways of doing this, but I was thinking one way
would be to use the eight buttons as a byte. This byte is split up
into a high "control" nibble and a low "data" nibble. The control
nibble has a write bit, a data type bit and a nibble type bit. This
determines what should be done with the data.

First, a high nibble of data is written. The vectrex shifts this
nibble left, and saves this to a RAM location, lets say $c881. Then a
low nibble of data is written. This low nibble is ord with the high
nibble and overwrites $c881. Thirdly, the address associated with the
data is written to the vectrex. The data byte which is now stored in
$c881 is loaded into B and the PSG register number is loaded into A.
This data is then written to the AY38912. Finally, $c881 is cleared,
ready for the next data byte.

I hope that all makes sense.

Anyway, so my problem is that I think it should be working, but of
course it is not. The main part of the code (ie. directly after the
header block) is posted below:

jsr CLEARSOUND

; MAIN PROGRAM
main
jsr WAITRECAL
jsr READBUTTONS
lda $c80f
bita #$80
beq begin_write
bra main

begin_write

bita #$80
beq data_type

address_type
ldb $c881
lda $c80f
anda #$0f
jsr SNDCHIP
lda #0
sta $c881
bra main

data_type
bita #$40
beq low_nibble

high_nibble
anda #$0f
lsla
lsla
lsla
lsla
sta $c881
bra main

low_nibble
anda #$0f
ora $c881
sta $c881
bra main