Badwolf wrote: ↑
Tue Sep 14, 2021 3:26 pm
Not quite following you on that one, I'm afraid. Can you run that past me again?
Have your Falcon running basically as a stock machine, but also have your booster board plugged in (without CPU even). then get your booster to decode the full ROM range and issue DTACK on a spare IO pin (not connected to system DTACK).
Then this spare IO pin will issue DTACK low on any ROM address on your scope. But also measure the actual Falcon side DTACK on your second scope channel. In fact measuring the motherboard ROM_CE probably be easier than DTACK..
So what will happen is, you have basically just a ROM decoder going on in your PLD, and you compare your "ROM DTACK" IO pin, with ROM_CE on the Falcon MB.
So what I'm saying is, your booster "ROM DTACK" should also match the ROM_CE Pulses on the motherboard ROM.. We can pretty much assume system DTACK will follow ROM_CE, but it is easier to just use ROM_CE for easy comparison with the ROM decoding in your PLD.
Being that this will check a lot of the address lines and your internal DTACK generating code. Obviously both signals should match perfectly. If there is a iffy address pin or something, then "ROM DTACK" on your PLD, will not always match ROM_CE on the Falcon ROM.