Current status @ deadline

A project log for wirez80

Z80 machine with a hex keypad and 7-segment displays built on a cylindrical wireframe

matsengmatseng 01/08/2019 at 18:300 Comments

Well, it seems that I will not have time to add any firmware before the deadline, but it can at least either run NOPs (if the display/keypad-module is disconnected) or was looks like $FF's when it's connected.

I reduced the clock speed to 28KHz to get the address bus LEDs to flash prettily.   

When the display unit is disconnected then the databus is giving just zeros to the Z80 when it runs and since 0x00 is a NOP for a Z80 it justs increments the addresses and fetches the next NOP all the way up to address 65535 when it wraps over to address 0 again.

By some reason the databus looks to end up as 0xFF when the display unit is connected and whatever instruction that is it looks like the addresses are decrementing instead. Maybe it's a relative branch to -1 that makes it go backwards? I haven't bothered to look it up yet.

So the Wirez80 seems to be in reasonably good working order, just lacking me writing some firmware for it. But that will take more than the 90 minutes remaning for the deadline so this is what y'all get from me this time. 

I will of course spend some more time on the project to get it in a more working order with a "monitor" firmware to examine/deposit data to the memory and run code.

The WireZ80 running dummy instructions
The WireZ80 running dummy instructions

I'll definitely need to make some kind of acrylics enclosure for it that will keep it safe or else it might end up all squashed as my old "Lethal Nixie Cube" did when I stepped on it.