LogicAnalyser

Using the software and hardware described here:

• on the TransferPC
• using the suggested 75HC245 to protect the parallel port.
• only 2 probes

I've used these settings to debug the audio circuits of the MEK6800:

• trigger channel: 1 (I wish I could disable triggering)
• pre-trigger delay: 0
• sample size: 2000
• sample period: 2 (this is the resolution, but don't set to 1)
• granularity (read only): 1.65 us.
• zoom: length 5.28 ms

Caveats:

• while sampling, you cannot interact with the PC at all!
• so be careful with continuous mode: you get a brief change to stop after each sample period (which can be long depending on the settings)
• the sampling first waits for a trigger, i.e. a transition on the trigger channel.