SN76489A frustration

[netdudeuk]

Hi

I bought some of these to give me sound output from a retro computer that I'm building.

I made a test setup connected to an Arduino but got no sound.

So, I got another chip out and took it down to the basics, with just a 4MHz clock and /CS low.

I've read that the chip should make an initial tone (as in the first of the BBC Micro power on bleeps) until told to be quiet.

However, the scope shows a sine wave at 431 kHz on the output.  At that frequency, I'm not expecting to hear anything.

When I was running the Arduino code, the frequency was about the same.

I disconnected the oscillator and fed in a square wave, going all the way down to 100kHz.  However, the output frequency remained pretty much the same.

Any ideas please ?

Thanks

[bitslice]

with just a 4MHz clock a

The SN76489AN has a maximum clock of 500KHz

The SN76489A has a maximum clock of 4MHz

Noted that you later changed the osc frequency, so dunno



Edit: you appeared to have changed your title from SN76489AN to SN76489A
would have been nice to acknowledge the edit in case people think I can't read :|