Z80 Playground part 3 (This is my Single Board Computer or SBC that runs Basic and CP/M)

Рет қаралды 4,751

4 жыл бұрын

Latest version of this project: kzfaq.info/get/bejne/g8efn7ed0J28e4E.html
In this video I check out the RAM and ROM memory mapping as well as the capabilities of the 16C550 UART.
v1.1 now available: kzfaq.info/get/bejne/r594gcV738rGoHk.html
Schematics: 8bitstack.co.uk
Full playlist: kzfaq.info/sun/PL3arA6T9kycptsudBx3MyLbHCOjdoBhO6

Пікірлер: 14

@akhurash 4 жыл бұрын

Interesting project.

@CircuitBreaker256 4 жыл бұрын

I think so too!

@albertpauw8234 4 жыл бұрын

Very interesting project. I've been using a Z80 system many moons ago, including CP/M so I'm interested how this is progressing. Looking forward to your first running CP/M. Are you planning on selling the board (when all problems are ironed out)?

@CircuitBreaker256 4 жыл бұрын

I did think about putting the board on ebay!

@15743_Hertz 3 жыл бұрын

If you want to add a cheap graphics card, check out PiGFX on Github. It uses a Pi Zero and ANSI escape sequences to drive either an HDMI or a composite output.

@CircuitBreaker256 3 жыл бұрын

I have already considered this option!!

@tracyscott3261 4 жыл бұрын

do you have a website? are you going to share the code?

@CircuitBreaker256 4 жыл бұрын

I'm working on it!

@RetroRogersLab 3 жыл бұрын

I'm curious why there's a need for NOPs after writing to the UART chip.

@CircuitBreaker256 3 жыл бұрын

I bet there is no need at all. I think it was some debugging code that is still left in there. What I actually found was, the UART seems to take slightly longer to wake up after reset than the processor does, so I had to put a short pause in the code AFTER reset and BEFORE configuring the uart. I think that in desperation to get it working I put pauses all over the place, and then left those ones in by accident once I'd got it working. I spent about 5 hours tearing out my hair over that one!

@RetroRogersLab 3 жыл бұрын

@@CircuitBreaker256 I asked because I've had issues with one of my 16C550 projects and was wondering if this was my issue as well. Thanks for the mentioning the reset delay.

@CircuitBreaker256 3 жыл бұрын

@@RetroRogersLab I discovered it by looking at the TX line on a 'scope. It was working in 5 bit mode not 8 bit mode, which turned out to be the default value if you don't configure it. So I figured that I had not actually configured it, even though my code was trying to do just that.

@RetroRogersLab 3 жыл бұрын

@@CircuitBreaker256 This has really got me thinking about my old project. I did some Googling and ran across this page: www.z80.info/z80sourc.txt. If you follow the init code it looks like they're using the UART scratch register to see if the UART is present but this might also work for is it 'alive'. I might give it a try this weekend and see if that solves my problem without NOPs.

@CircuitBreaker256 3 жыл бұрын

@@RetroRogersLab ah, thats a good idea. Keep writing to the scratch register and reading back until you are sure the 16c550 is awake, then configure it. I'll use that idea. All I did was a huge delay loop at start up.