Progress with PSRAM and Intel HEX uploader in Verilog

A project log for vector-06c mini

A 50% size replica of my favourite 8-bit computer

svofskisvofski 04/16/2024 at 22:140 Comments

So although the last update already had a lot of promise, the machine could not really survive much farther past the initial boot screen. After a couple of days of juggling around with various priority combinations and delays trying to squeeze memory accesses with PSRAM clocked at 48MHz I decided to finally give 72MHz a try. First attempt worked, but seemed flaky. After some trial and error I found a delay that seems to work well, at least mostly.

Now it's not ideal yet. There are sometimes video ram accesses that don't make it just in time. So it's subject for a deeper scrutiny later. I already found one program that fails terribly. And of course there's the eternal bane of all things Vector-06c: palette register write delay. When it's off, it looks like this:

There should be no large gap between the white text block on the left and the rainbow bars. But it's still a huuuuuge progress and I'm happy.

There's also one thing that I developed to help debugging this and I really like it. It's a very basic console debugger: you can press ctrl-c to stop the machine, then press "c" to continue. That wouldn't be much, but there's one more thing. You can paste an Intel HEX file in the terminal, and it will be written to RAM. Not bad.