I'm planning to buy a Z8018006PSC. A z180 CPU (which I found is compatible with the z80 and has some advantages, for instance, able to address up to 1MB of RAM).

I'm planning to use it together with a 3.3v FPGA to generate its clock (so it can be "variable").

I just want to know if I'm reading the documentation right. On the absolute maximum ratings it can be run from -0.3v to +7.0v. So I can drive directly with 3.3v? And the input ports have a tolerance of vcc + 0.3v, so at 3.3v i will be able to put up to 3.6v on any input port?

Of course, it will not run stably at 6MHz, but something close to 1MHz~2MHz will be fine for my purposes.

  • This isn't a retrocomputing question, it's an original electronic design question. Jul 22 '17 at 13:07
  • 1
    The z80 family of microprocessors are still used heavily in modern devices such as calculators. What are you planning to use this for?
    – wizzwizz4
    Jul 22 '17 at 19:50

This data sheet http://www.datasheetspdf.com/datasheet/Z8018006PSC.html (page 189 of the PDF download) gives the DC operating conditions for a supply of Vcc = 3.3V plus or minus 10%, as well as 5.0V plus or minus 10% (on the preceding pages).

The AC characteristics (page 193) are also specified at both 3.3V and 5V.

From a quick reading, the maximum clock frequency at 3.3V seems to be 20MHz, compared with 33MHz at 5V.

Note: as @mcleod_ideafix said in a comment, 3.3V operation is only supported for the Z8L180 version of the chip, not the Z80180 version.

But if the OP wants to use 3.3V operation and hasn't ordered the part yet, ordering the correct version would be a more reliable option than hoping the 5V version will work at reduced voltage and/or reduced clock speed.

  • 2
    Careful! 3.3V operation is supported only for the L version: Z8L180. Z80180 is not the L version. May 1 '17 at 13:44

Absolute maximum ratings are the minimum and maximum voltage the device can withstand without damaging. They aren't the minimum and maximum voltage the device is operative at. Those are the "recommended supply voltage". Beyond these, the manufacturer cannot assure the functionality of the device although as long as the supply voltage is within these absolute maximum ratings, the chip won't be damaged.

If it is a NMOS device, you won't probably be able to make it run properly at 3.3V . On the other hand, I've been able to power a CMOS Z80 rated at 20MHz at 3.3V and used succesfully with a FPGA clocking the CPU at 3.5 MHz. CMOS devices seem to be more forgiving about supplies as long as you slow down the clock if the supply voltage is lower than the recommended settings.

  • As the above answer suggests, the Z180 in question actually is specified at 3.3V - but +1 for explaining AMR vs operating voltage... May 2 '17 at 11:44
  • Actually, it's not. The datasheet covers several versions of the Z180 chip, and the one the poster is intending to use is not rated for 3.3V. That's something I've warned about on a comment to the chosen answer. May 2 '17 at 11:56

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