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Thread: Z80 - can it be controlled like the 8080 with a control panel?

  1. #1

    Default Z80 - can it be controlled like the 8080 with a control panel?

    I found this on the web, but I don't know how it turned out:

    https://electronics.stackexchange.co...t-panel-design

    I figure the S-100 folks probably know very full the ins and outs of this.

    I have a couple of questions:

    Does the M1 signal only occur at the beginning of a sequence of fetches? For example, if you have a 4 byte instruction, does M1 only go low at the first fetch?

    I saw that wait can be used to extend the fetch.

    Has anyone made an actual control panel for a Z80?

  2. #2
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    There were several Z80 S100 cards that were made to work in the Altair 8800 box without modification. Many even had the header for the Altair status line cable. So yes.

    But there are several status signals such as IE (interrupt enable) that do not display on the panel. But as far as examine, deposit, single-step, yes.

  3. #3

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    That is interesting. I saw a modern Z80 trainer than someone made on eBay. It has some 7 segment displays and a keyboard for entering data, storing, examining, etc. At first I was assuming that it was like the control panel on an Altair, but after looking at it closer, it is more of a software control panel that interacts with code running on the Z80 itself. I am presuming he has a monitor written for the Z80 that interacts with the keyboard/7 segment displays. This is unlike the Altair CP which was a true hardware CP requiring no CPU side code at all.

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    Sure, the Altair (and IMSAI) front panels pretty much show the status of the S100 bus and have a bit of circuitry for single-stepping and data entry/display. You could really go to town and design one with breakpoint facilities, for example. That would be handy.

  5. Default

    Quote Originally Posted by Chuck(G) View Post
    Sure, the Altair (and IMSAI) front panels pretty much show the status of the S100 bus and have a bit of circuitry for single-stepping and data entry/display. You could really go to town and design one with breakpoint facilities, for example. That would be handy.
    The IMSAI front panel went through a number of revisions (likely some were "accumulated wisdom of the field" and not official) to deal with various things not envisioned in the original IMSAI board set. Mine had a variety of hacks to deal with memory boards using "Semi 4200" chips (you could actually load code into that RAM in a system with a disk drive, then pull the board out and put it in a different box and hit "continue" and the contents would still be there!) and the Digital [Micro]Systems floppy controller interface card, which did things to the bus IMSAI never imagined.

    Back to the original question - Ithaca Audio (later Intersystems) had a Z-80 CPU board and matching front panel.

  6. #6

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    I have a North Star ZPB-A1 "Z-80 Processor Board" with a 16-pin connector for a control panel. It has a Z-80A and to QC stickers showing the board tested ok in June 78. If I remember correctly, this plugged right up to my IMSAI front panel. This board had a PROM option available but this paticular one doesn't have it installed.

    Here's a PDF copy of the manual for the earlier ZPB-A:

    http://www.hartetechnologies.com/man...r%20Manual.pdf
    Last edited by cchaven; May 13th, 2018 at 04:08 PM.
    Collection online nonstop since May 1997: http://www.cchaven.com

  7. #7

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    I have a vague memory that my IMS 8000 has a header on one of its S100 boards meant for a front panel, and maybe some jumpers to that effect? I'll have to check the manual but I'm sure I remember reading it had that facility should it be required. Not sure to what extent it would be like an Imsai or Altair front panel though.

    I also have a Z80 trainer board made by Polar Instruments that has a numeric keypad, 7 segment led display - the ability to input simple instructions. Dates from 1990 I think so quite a late entry.

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    Yes, as I said--early Z80 cards had the header also. My Z80 card does--I think it's from SD Systems, but I'd have to go digging to verify that.

    Most Z80 cards with headers don't provide some of the status signals, such as interrupt enabled, as it's not present as a Z80 external signal. That was a disappointment for me, early on, as I tied a capacitor to the front panel LED and then to an audio amplifier and used EI/DI instructions to make music with the 8080 card.

    Example

    Looking at the card shown, mine is different--it has a 2708 EPROM on it. Maybe it's a "Digital Research: Computers" board or some such.
    Last edited by Chuck(G); May 22nd, 2018 at 05:35 PM.

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