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Thread: Building a homebrew Z80 board

  1. #11
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    Wire wrap is no good for analog, RF, surface mount, etc.

    But for playing around with DIP packaged digital ICs, it is ideal.

    You don't have to use a CAD system (sounds too much like work ), and then wait a week to get boards. You can throw something together in an afternoon. Later you can add or change your design easily.

    The cost of sockets and wire is a little high, but with a handful of chips like you are describing the difference isn't much. You can use a hand wrap tool. It can be fun.

    A lot of the home-brew CPU guys use wire wrap, for example: http://www.bigmessowires.com/2009/05...oject-summary/

  2. #12
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    Quote Originally Posted by xprt View Post
    Wire wrap is no good for analog, RF, surface mount, etc.

    But for playing around with DIP packaged digital ICs, it is ideal]
    I do my wire-wrap over a ground plane and have even used twisted-pair for ECL (lots of ECL boards were wire-wrapped and that's about as close to analog as you can get in logic). My boards typically are single-sided foil FR4, with bare 20 AWG wire on the top side running with bypass caps every inch or so between IC rows carrying +Vcc, the foil side, of course, is ground. I get very good HF performance on that setup. SMT can be accommodated with inexpensive adapter boards (my current project uses a PIC32 100-pin TQFP).

    Wire-wrap's like anything else--a lot of it depends on technique.

  3. #13
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    I agree that with good technique you can do amazing things with wire wrap.

    My thinking about analog and RF was imagining a lot of discrete parts. With RF people often just solder stuff together with minimal lead lengths on to a ground plane, something like this:


  4. #14
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    Project on hold until I get hold of parts.

  5. #15
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    Quote Originally Posted by xprt View Post
    I agree that with good technique you can do amazing things with wire wrap.

    My thinking about analog and RF was imagining a lot of discrete parts. With RF people often just solder stuff together with minimal lead lengths on to a ground plane, something like this:
    Looks awesome until you have to do it that way.

  6. #16
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    Quote Originally Posted by xprt View Post
    I agree that with good technique you can do amazing things with wire wrap.

    My thinking about analog and RF was imagining a lot of discrete parts. With RF people often just solder stuff together with minimal lead lengths on to a ground plane, something like this...
    Now why does your photo make me think of the late, great, Bob Pease?

  7. #17
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    Quote Originally Posted by Crypticalcode0 View Post
    Looks awesome until you have to do it that way.
    I've done it before and it worked up to 2GHz. But I cut some little double sided board pieces soldered down for stand-offs to be a little more mechanically secure than this picture. OK for something literally quick and dirty.

    Quote Originally Posted by Chuck(G) View Post
    Now why does your photo make me think of the late, great, Bob Pease?
    Somehow the same thing came to my mind a little later, too. Maybe it was remembering this picture:

    http://www.rfcafe.com/references/ele...breadboard.htm


  8. #18
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    Aaarghh... now that's truly a rat's nest!!

  9. #19
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    OK I have some parts now.

    I am using an Arduino for testing. First I tested the SRAM and I was able to read and write to it with no issues.
    Now I connected the Z80 to the Arduino programmed to emulate a EPROM.
    I connected a PUSHBUTTON along with a pull down resistor to the clock pin.

    I programmed the Arduino to output 4 NOPS followed by a jump to address zero.

    I then watched the serial monitor output of the Arduino which shows the current Z80 address. When I pushed the button I watched the addresses count 0->1->2->3->4->0. Yeah! Its working..

    Now I need to make it standalone.

    First problem is I do not really know Z80 ASM. Secondly, the z80asm assembler is not accepting my code.

    For example I try to assemble:
    Code:
    LD (0),0
    Which I thought would load the value zero into address zero but it give me:
    Code:
    Assembling....
    test1.z80:1: error: parse error. Remainder of line=0
    *** 1 error found ***
    So I try
    Code:
    LD (A),0
    but I get the same error.
    I then tried
    Code:
    LD (A),A
    and I got
    Code:
    Assembling....
    test1.z80:1: error: unable to resolve reference: A),A
    *** 1 error found ***
    Can someone please help?

  10. #20
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    Have you looked at the documentation?
    Here: http://www.nongnu.org/z80asm/expressions.html
    and here: http://www.nongnu.org/z80asm/directives.html
    the first links says that this assembler is sensitive to parenthesis...
    Torfinn

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