test of SID not working

MIDIbox SID
1

Hey,

I got my hands on two SIDs 6581 and I wanted to test them using an AVR chip I had lying around.

However, the SID isn’t making any sound: I have my oscilloscope hooked up to the OUT pin. All I’m getting

is some low noise on a ±7V DC level. The DC level seems to match the datasheet.

I used the same setup as the MBHP_SID: two 74hc595’s connected to data and address pins, R/W to gnd,

the clock is generated by the microcontroller at 880kHz (verified with the scope). I had the clock at 1Mhz before,

but I lowered it just in case it was going slightly too fast.

I reset the SID before sending my data. It remains high the rest of the time.

After setting the address and data, I put CS low for 1ms (far more than required). I also keep it high for 1ms+.

I set the following registers:

Voice 1 freq = 0x4189

Voice 1 control reg = 0x11 (triangle + gate)

Voice 1 attack and decay = 0x00

Voice 1 sustain and release = 0xF0

RES/filt = 0x00

Mode/Vol = 0x0F

I’ve been looking at this for a while now and have no clue what is going wrong.

The data and addresses have been verified as well as the clock and chip select pins.

Any clues or tips?

Kind regards

Tom

2

I recall raising the sustain level after the gate is on will cause the sound to stop.

If you’re setting the registers in the order you wrote, then that might be why there’s no sound. Set the gate bit last, if you’re not doing that already.

3

Oh boy,

I’ve been looking at the circuit and the timings so hard that I missed that obvious fact.

Alright, after that quick fix I got a nice little triangle wave coming out of it :slight_smile:

On to the next bit..

Cheers

4

Great! :slight_smile:

Best Regards, Thorsten.

5

I can’t believe that was the problem…  :o