I have various Z80 CPU's in my parts bin. Some are from Zilog and some are from other companies (IIRC). Some of them are hard to see the part numbers so I can't tell who made them but I'm sure they are Z80's.

Anyway, I need to build a circuit that uses the Z80 as the primary CPU (mini-computer) but I want to connect it to 3.3v devices like the propeller or other microcontrollers.

I've looked in various datasheets that I can find but none of them mention if the CPU can be powered from 3.3v. I read they can "tolerate" -0.3v to 7v on all input pins but nothing (that I can find) says they can be driven by a 3.3v power supply.

The frequency I would like to run the CPU would be the NTSC colorbust frequency of 3.57954 MHz but it could go as high as 4 MHz.

Thanks for any information.

  • 2
    \$\begingroup\$ The definitive answer is in the respective datasheet, however NMOS parts probably won't work at all at 3.3V, newer CMOS ones may work, at some speed. \$\endgroup\$ – Spehro Pefhany May 1 '15 at 13:26
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    \$\begingroup\$ This is a dumb question since it is directly and clearly answered in the datasheet right where you'd expect to find it. \$\endgroup\$ – Olin Lathrop May 1 '15 at 13:56
  • \$\begingroup\$ I looked in the datasheet. If I expected to find it there (which I did), but DIDN'T find it there, then I obviously overlooked it. Hence, the nature of this question. In fact, it's all in the datasheets. Every answer. So why have this site at all. \$\endgroup\$ – cbmeeks May 1 '15 at 14:57
  • \$\begingroup\$ This project is a reverse engineered z80 that runs on modern FPGAs opencores.org/project,a-z80 \$\endgroup\$ – jbcreix Feb 16 '16 at 8:18

The datasheet says Vcc= 5 V ±5%.
At the time the Z80 was introduced 3.3V logic was completely uncommon (if not non-existent).

Cf. this table about different logic families, typical supply voltages and year of introduction.

The Z80 dates back to the time when TTL-LS (low-power-Schottky) was common.

  • \$\begingroup\$ I was afraid of that. I must have missed that in the datasheet. Do you know if there is a 3.3v version of the Z80? Thanks \$\endgroup\$ – cbmeeks May 1 '15 at 13:31
  • \$\begingroup\$ I know that later there were/are CMOS versions (e.g. from Hitachi). Maybe some of them can run on lower voltages, I'm not sure though. YOu have to find the datasheets \$\endgroup\$ – Curd May 1 '15 at 13:39
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    \$\begingroup\$ There are also more modern controllers containing a Z80 core (i.e. CPU + some peripherals and memory on-chip; not just a plain Z80 CPU). They probably run at 3.3V. \$\endgroup\$ – Curd May 1 '15 at 13:47
  • \$\begingroup\$ Do you have an example of one? \$\endgroup\$ – cbmeeks May 1 '15 at 14:03
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    \$\begingroup\$ e.g. Zilog "Z8 Encore!" \$\endgroup\$ – Curd May 1 '15 at 14:35

I have a video showing an original Z80 8Mhz chip running happily at 3.3 volts. - it 'conked out' at 3.1, ran reasonably well at 3.2, I'll be running it at 3.5 hooked up to a Pi :) - Facebook Zilog z-80 DIY group.

  • \$\begingroup\$ Rephrase your answer so that it looks more like an engineering test report and less like a Facebook post, please. \$\endgroup\$ – Nick Alexeev Nov 24 '18 at 20:03
  • \$\begingroup\$ Second word is off, you choose the first. \$\endgroup\$ – Cassion53 Feb 24 at 21:39

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