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I would like to create a 20Mhz clock that generates a square wave for the home-brew Z80 computer I' making. I already have several 20MHz crystal oscillators but am at a loss when it comes to circuit diagrams and other components needed. I have looked around but I haven't found any diagrams with all of the details that I need.


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Are you sure your Z80 can run at 20MHz? The fastest version I am aware of was Z80H, which ran at 8MHz max. – jippie May 8 '14 at 18:52
The one I bought is in fact the 20MHz model – VivaDaylight3 May 8 '14 at 19:02
@jippie it goes up to 25 MHz; see the end of this page z80.info/z80brief.htm – Cornelius May 8 '14 at 19:13
@Cornelius I wasn't aware of those advances. Last time I checked the Z80 datasheets there was no such thing as SMD or QFP and I thought development was discontinued after the 8MHz version. – jippie May 8 '14 at 19:20
@jippie neither did I, but I found it in that link. – Cornelius May 8 '14 at 19:21
up vote 3 down vote accepted

You will need a 74 series IC (7400, 7404, 7406 etc.), two capacitors and two resistors.

Here is one possible circuit for a square wave clock generator:

enter image description here

Source: z80.info by Thomas Scherrer. Also check his site for more Z80 related information.

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If you have a crystal oscillator (they usually come in a 4-pin can), you just have to apply power (and ground) to the oscillator, and it will produce a 20 MHz square wave, which can be fed directly into the Z80's clock input.

If you have a plain crystal (usually in a 2-pin can), the other answers show possible oscillator circuits.

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