... I've got a Z180 setup which has to run at a very nonstandard 23040 baud while running at 3.686 MHz ...

That's very tidy! Is there a way to set the clock divider so it could have the option of running at 3.579545 MHz while still having a normal serial baudrate? I'd like to play around with old Coleco or MSX game stuff, which used a Z80 at that frequency. I've got a Z180 setup which has to run at a very nonstandard 23040 baud while running at 3.686 MHz (close enough to 3.579545). I'd be interested in one if Coleco/MSX speed isn't too much work.

BTW I saw you finished your ZZ80MB EEPROM programmer code, so I got that set up on mine. Very nice to be able to bootstrap from EEPROM now.

I hope you'll come back to the 68030 stuff. I'd love to see the CB030 evolve into something supporting ethernet and storage. I haven't touched mine since I got the linux demo running on it, sadly.

The much bigger question is whether Z280 is compatible with MSX. If you don't use Z280's internal functions like UART, timer, DMA, MMU, OK, it is more likely to be compatible, but then it is no better than a Z80.

Very nice design, indeed. Although I miss the RTC chip, needed for CP/M 3, MP/M, UZI280 and RSX280.

So, this is the board I've really been waiting on. Like I originally said in my thread that morphed into the CPU280 revival thread, I have always wanted a Z280 speedup board for a TRS-80 model 4. Well, with a few modifications, ZZRCC is that board. The RC2014 bus, with a little bit of work, can interface back to a Z80 socket easily enough. I've booted a ZZRCC here, and now to design the modifications to make it drive a Z80 socket.

Very nice design, indeed. Although I miss the RTC chip, needed for CP/M 3, MP/M, UZI280 and RSX280.

Interesting you should say that. Since ZZRCC does have an I2C interface, I'm just thinking about a small I2C board with RTC and stack-able 4-pin connector so the 128x64 OLED display can plug on top of it. The purpose is a clock where RTC provides the time base and 128x64 OLED the clock face. Will such a board serve your purpose, or do you also need an interrupt associated with it?

While it's nice to have, CP/M Plus doesn't have to have an RTC chip.

dittman wrote on Mon, 11 January 2021 20:50

While it's nice to have, CP/M Plus doesn't have to have an RTC chip.

True, but if can have a feature you will want to have it . Without an RTC CP/M 3 will not have timestamps, and utilities like 'make' will not work. Yes, you could still maintain the TOD using timer interrupts, but is annoying having to enter the time and date every time you (re)boot the system. But the Z280 is a bit overkill for CP/M 3 anyway; it really shines in multitasking, and with multitasking OSes an RTC is normally a must.

You may have tight space to work with, if so I can easily redesign the board to suit your application. Heck, if you've been wanting to do that all these years, I'm sure there are many other TRS-80 fans on VCFED that'll also be interested. So let me know what you need, I'm happy to help.
Bill

plasmo wrote on Mon, 11 January 2021 20:58

You may have tight space to work with, if so I can easily redesign the board to suit your application. Heck, if you've been wanting to do that all these years, I'm sure there are many other TRS-80 fans on VCFED that'll also be interested. So let me know what you need, I'm happy to help.
Bill

Wow. Let me think about this; I want to be very careful to not overcommit here....I've done that before, and caused some problems this past year.