Z80-Inside-2-300x278.png
It seems like everyone is doing something with the Z80 so I need to scratch my Z80 itch by jumping in too. :)
I may look into my Diving Deeper (https://savagechats.com/index.php?topic=372.msg1752#msg1752) project. It stalled out when I saw the complexity of opcode circuitry.
@granz mentioned the fpga (DE0-Nano) I put the ZX81 on. I have found the source code so I need to work on wiring up a PS2 connector and a transistor video driver to get it working again. I'll post it on the projects page. It is based on the ZX-Gate (https://zxgate.sourceforge.net/) which is code for the ULA by Bob Wenzel with the T80 (https://opencores.org/projects/t80) a Z80 softcore. the link to the ZX-gate's source is missing the code but I have a copy that I can post here if anyone is interested.
Since my free time is scarce I plan on working on a ZX81 on a DE10-Lite through this year. The ZX-Gate uses VHDL and I am more familiar with Verilog so I rather do one with Verilog using the A-Z80 (https://github.com/gdevic/A-Z80) soft core.
I am in the researching phase looking at other soft cores I found and Chat-gpt. I have a tendency of thinking big then jumping in and losing steam as I go along so I hold myself accountable to all of you to see this project through.
Quote from: MicroNut on Jan 20, 2026, 07:34 PMIt seems like everyone is doing something with the Z80 so I need to scratch my Z80 itch by jumping in too. :)
I find it interesting that interest in the Z80 worldwide has peaked a little since Zilog discontinued it.
Quote from: Chris Savage on Jan 21, 2026, 09:36 AMI find it interesting that interest in the Z80 worldwide has peaked a little since Zilog discontinued it.
Yeah, it is pretty interesting, but it kind of fits in with the laws of supply and demand. Zilog quits manufacturing the chips (although they are still manufactured by second source providers) and the supply is perceived as going lower, thus the price (or rather the interest in this case) goes correspondingly up.
Yes, very interesting - and I still want to build some Z-80 system (however the RunCPM, and the RP2040-GEEK & Udo Munk's Z80Pack on the RP2350-GEEK (https://savagechats.com/index.php?topic=514.0) may scratch that itch for the time being.
Nothing like the real thing, though, right?
Quote from: granz on Jan 21, 2026, 01:04 PMNothing like the real thing, though, right?
Having programmed the 65xx, 68xx, 680xx, 68HC11, 808x and the PC, I found that I loved the Z80 assembly the most. If you're a programmer and want to mess with the Z80 for CP/M, BASIC or Assembly, it doesn't really matter which platform you're on.
fig_2-1.gif
For me, I found the hardware interface as attractive as the software. To drop a Z80 in the middle of a breadboard (https://savagecircuits.com/z80-retro-computer/), or a perf board using wrapping (https://savagecircuits.com/z80-control-board/) as I used to, and then start hanging RAM, ROM and I/O off the CPU is extremely fun for me. I really enjoy it.
I enjoy trying to connect hardware that is both directly compatible with the Z80 (such as the 8255 PIA), as well as hard that is
not directly compatible (such as the HD44780 LCD), forcing me to create glue logic to facilitate the interface; all the while having to write custom routines to handle the various pieces of hardware.
I have quite the library of routines now for keyboards, LCD, speaker output, PIA, UART, IRQ / NMI and even RAM testing and ROM checksum calculation. But back when I wrote these, everything was serial or parallel. Now I use more I
2C and SPI devices than parallel. To that end I'm looking forward to writing a Z80 SPI routine and being able to use these devices as well as the parallel stuff.
Z80-shirt-front.jpg
Quote from: Chris Savage on Jan 21, 2026, 01:41 PMZ80-shirt-front.jpg
I like it - where did you get this?
Quote from: granz on Jan 21, 2026, 02:30 PMI like it - where did you get this?
I don't
own this shirt...
yet. But I found it on the website for The 8-Bit Guy (https://www.the8bitguy.com/product/t-shirt-z-80-processor-in-royal-blue/).
I agree with Chris, it is fun to wire chips up to the Z80 like the 8255. I put a 8522 on a Timex Sinclair to read one of those old Atari joysticks and hacked a copy of Frogger to read the 8255. I found a site where an Arduino was wired to the Z80 with a very slow clock rate so the user could decipher the functioning of the Z80 for certain opcodes.
Quote from: Chris Savage on Jan 21, 2026, 02:47 PMQuote from: granz on Jan 21, 2026, 02:30 PMI like it - where did you get this?
I don't own this shirt...yet. But I found it on the website for The 8-Bit Guy (https://www.the8bitguy.com/product/t-shirt-z-80-processor-in-royal-blue/).
Sad, the only size that they are showing is XXXXL (as they said:
extra extra extra extra large ::) ) and those are out of stock. :(
Eighteen dollars is not bad, and if they come back, I may get one.
Quote from: granz on Jan 21, 2026, 03:07 PMSad, the only size that they are showing is XXXXL (as they said: extra extra extra extra large ::) ) and those are out of stock. :( Eighteen dollars is not bad, and if they come back, I may get one.
I will contact him later tonight to see what his plans are on these.
P.S. - Did you see the "back" of the shirt?
Z80-Blue-overhead-back.jpg
Quote from: Chris Savage on Jan 21, 2026, 03:13 PMQuote from: granz on Jan 21, 2026, 03:07 PMSad, the only size that they are showing is XXXXL (as they said: extra extra extra extra large ::) ) and those are out of stock. :( Eighteen dollars is not bad, and if they come back, I may get one.
I will contact him later tonight to see what his plans are on these.
P.S. - Did you see the "back" of the shirt?
Yes, and it made me look at Amazon for custom printed T-shirts. I was thinking of putting an entire Z-80 (or something) schematic onto a shirt. 8)
Quote from: granz on Jan 21, 2026, 06:13 PMYes, and it made me look at Amazon for custom printed T-shirts. I was thinking of putting an entire Z-80 (or something) schematic onto a shirt. 8)
Oooooh! 8)
I initially forgot to contact the 8-bit guy, but I remembered today after seeing the thread being perused (most likely by a bot), and it reminded me to email him. I'll follow up if / when I get a reply.
The 8-Bit Guy got back to me. Good news...
QuoteI'm working on a new design... but yeah, eventually I'll have Z-80 shirts again.
Quote from: Chris Savage on Feb 18, 2026, 09:06 PMThe 8-Bit Guy got back to me. Good news...
QuoteI'm working on a new design... but yeah, eventually I'll have Z-80 shirts again.
That's good. I emailed him once, never got back with me.
It's not what you know, but who you know that counts. :P