For those following progress of my IntegraB V2 project:
With the help of some very knowledgeable and helpful people on this forum (you know who you all are!!!) I managed to get both Shadow and SWRAM / ROMs working reliably on my board. However, currently I am having to use a bunch of 32K RAM ICs instead of the 512K IC that is soldered onto the board.
The 512K IC does work to a degree, and I can both read / write to it without any issue. However, if I try to run code from it, it's not so happy. For example, if I load BASIC into one of the banks (using Martin Barrs EELOAD utility), it loads and verifies fine. On reset it even responds correctly and returns with the
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BBC Computer 32K Acorn 1770 DFS BASIC >
On my 512K IC, I've added a MAX6366 Supervisory IC to the /CE line to try and avoid data corruption on power down, and I suspect this is the source of the problem. I've wired A13 into the watchdog input, but on reflection that was probably not the wisest choice. I picked that line because it was easy to route on the PCB.
So, before getting the soldering iron out, my question is - should this work as I've designed, or have I missed something altogether here? Do I just need to use a different address line (like A0) which is probably going to be toggling more frequently, or should I scrap this idea altogether and just get the CPLD to drive /CE directly?
Once again TIA.