Guidance on troubleshooting a bus problem

Tool suggestions, soldering tips, general useful electronics knowhow.
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Joined: Thu Nov 12, 2020 5:58 pm

Guidance on troubleshooting a bus problem

Post by Wrangler » Sun Nov 15, 2020 6:13 pm

Hi folks, I'd welcome some guidance on troubleshooting a bus problem. The best tool to use it and how.

I'm working with some of the guys on A1k to try to get the DSP working on the replica Amiga AA3000+ motherboard. (This is a modern remake of the AA3000 prototype that had a DSP3210 on it but was never released.) Bus control is managed through some GALs. As far as I can work out, bus arbitration works and the DSP is granted the bus but for reasons I don't understand a 68030-compliant address strobe is never generated by the GALs. Result: machine freezes waiting for a memory read that never happens. DSP clock is 50MHz btw.

I don't have an oscilloscope or a logic analyser. A LA seems to be the better tool for the task of really seeing what's going on before the hang but is £££. A 100MHz 2 channel digital scope would be cheaper, but gives you less info. Thoughts?

Even after sorting that out, I am concerned with attaching the probes to the motherboard. There are no useful attachment points that I can see. So only answer is to solder thin wires to the relevant tracks/pins. Not sure my soldering is up to that. Any alternatives?

Happy to add more detail, but that's the gist of the challenge! Would welcome any insights from the pros! ;)

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