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Elaborate Reset Circuit

October 17, 2015

On an AVR I can usually get away with shorting the reset pin to ground with a tact switch aith a pullup to +V and a cap if i’m feeling generous. The poor thing probably resets multiple times but no harm. The Z80 is a bit more finicky.
15-10-16 reset circuit breadboard

The circuit is based on http://www.z80.info/gfx/z80test.gif with the addition of a Schottky diode between the second inverter and the reset pin. The diode is needed because the power on reset circuit on the cpu board has to be able to pull down the reset pin during power up independent of what this button is doing.

15-09-27 reset circuit

CPU Board power on reset circuit.

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From → Olduino/Z

5 Comments
  1. inaxeon permalink

    Can I suggest you save yourself a tonne of hassle and replace that with one of these? http://datasheets.maximintegrated.com/en/ds/DS1232.pdf

    • inaxeon permalink

      (I’ve got one on a Z80 alarm clock I dummied up a while back)

    • Oh, that’s an excellent idea. Thanks. I could also think about an 8 pin Abe that could do some clock generation in its spare time.

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