Clearly I’m getting rusty!

In the Christmas break I’ve finally found a little bit of time to tinker with FPGAs again.  Not enough to tackle anything major, but I’ve done a little bit of bug fixing on the OneChipMSX core.

Or so I thought.

A problem with the OneChipMSX core on newer MIST boards was brought to my attention, and when it became clear that the affected boards all had a different revision of SDRAM chip that’s where I started looking.  I thought I had timing constraints for the SDRAM in place, but it turns out that wasn’t the case, so having added constraints I built the core, sent it to a tester who had both a new and old revision board, and was told all was well.

I’ve since had a report that the new version has problems with disk errors once MSX DOS is booted, and while I can’t reproduce that problem with the released revision of the core, I’ve since made some changes to reset handling so that it’s finally possible to hard-reset the core and clear a loaded ROM without power-cycling – and now I can’t build a core for the MIST that doesn’t give MSX DOS errors!

Building for DE2 results in a core that works just fine.  Building for DE1 results in a core that hangs on loading the BIOS – which is exactly the symptom the newer revision MIST boards were showing – but I don’t have any block RAM left so I can’t use SignalTap to diagnose it!

So clearly I’m getting rusty!  I’m hoping I’ll find time before going back to work to figure out what’s going on!

One thought on “Clearly I’m getting rusty!

  1. Welcome back! (*)

    (*) well, actually, this is *your* blog, so “welcome back” is somewhat odd – but no other catchy phrase comes to my mind that means “it’s really nice to see that you found some time for your FPGA projects!”

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