Issues with RAM expansion card 1.5

Hardware
1

I’ve now built a RAM expansion card, version 1.5. However, I cannot get it to work completely. I hope you can give me some tips.

The mainboard is a Planck 1.5 with power supplied via the barrel jack (7V, 1A if that’s relevant).

If I put the card in Slot 1, I can activate it with expad (HEX FF90 expad). I then select the first bank with 80 bank. I then dump the first 100 bytes of the RAM with 8000 100 dump. The data is different than if I run the command without the RAM card, so this makes me think that the RAM card has been swapped with the ROM. So far, so good.

However, I am unable to write data to the RAM. I have tried 8000 100 FF fill and 8000 100 erase. I then review the contents at $8000 with 8000 100 dump. No data is changed. All of these commands are with hex set as the base.

Am I misunderstanding how to write to this RAM?

Any ideas about what I should check next would be greatly appreciated. Thanks!

2

Strange bug. I’ll have to take a look, but it sounds more like a hardware problem to me. I won’t be able to test it since I don’t have the latest RAM board PCB. You really are on the bleeding edge!

3

LOL. Yes, I’m on the bleeding edge. I should have waited for you to build one before making my own.

If it’s a hardware (soldering, etc.) issue, then I’m not able to figure out what it is. I’ve built two RAM boards and they behave the same. I’ve done some basic tests of the logic ICs and they all function. Most likely, I need to mess with the surface mount RAM IC again, but I’m surprised that both boards would show the same problem.

Oh well, life on the edge! Have a good Friday.