James OtsI have banked memory working!
And on the way, I have discovered one of the reasons I've been having so much trouble. And it is that the FT245RL seems to get its knickers in a twist when I upload a new configuration to the CPLD, so I have to turn the board's power off and on and then everything works properly again. Not knowing this has wasted so much of my time!
But now banked memory appears to work. I've written a bootstrap programme which loads data from the FT245RL into RAM and then runs that programme. My test programme just switches the buzzer on and off each time you press a key. But it works.
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This also means that it actually works just fine at 4MHz, and seems to be fine with 8MHz too. In theory I could run it at 10MHz, but as I have a 16MHz crystal it's not so easy to do!
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I spotted the RESET pin of the FT245 isn't connected on the SparkFun breakout board, so I bodged it so that on of the breakout pins is now connected to reset instead of VUSB (which I never use). It now resets the FT245 when the Z80 is reset, but the FT245 still stays in a messed up state.
I guess it's not very important — I can always cycle the power every time I reconfigure the CPLD anyway.
Are you sure? yes | no