P Todd Decker single step for Membership Card

Last updated July 11 2010. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Contact Herb at www.retrotechnology.com, an email address is on that page..

In May, Todd Decker reported to Lee Hart, that he had trouble with the OUT 5 or OUT 7 instruction to feed data to the LED latch. So he built a single-clock stepping circuit to check out the design. This page describes the design and use. For the discussion of how Todd and Lee debugged the OUT circuit, check this linked Web page. The Intersil 1802 data sheet is on this site as a PDF file at this link. - Herb

May 15, Lee Hart: Here's how it's supposed to work during the 1802's the execute cycle of an OUT 5 (or OUT 7) instruction. See if you can track through this to find out why yours isn't doing this. - Lee Hart --

July 2: Here is a link to a short videoshowing a working set-up for single-stepping the membership card. I got everything set-up tonight and will tackle actually trying to figure out why my OUT 5/7 instruction isn't latching anything either Friday night or Saturday. I hope you guys forgive the corny video, but I wanted you to see things working.

I've also [created these images:]

The first is a quick circuit diagram of the [single stepping] set-up I'm using.
The second is a non-ASCII art version of the timing diagram.

Lee--Could you double-check the timing diagram for me?

Herb--Please do feel free to publish these onto the excellent web page you are building. Since I just breadboarded it out, it isn't really an upgrade but I suppose someone else could adapt it into a more interesting design. Perhaps even putting a down counter on it preset to the number of clock steps needed to truly step from one instruction to the next. But, I believe I recall seeing a more proper "single-stepping" circuit that could be used for this type of purpose. - P. Todd

Lee Hart: "Connect your external bounceless pushbutton to pin 13 of the 4093. This over-rides the 22pf capacitor C1 and resistors R1 and R2."

Todd, July 16:I finally was able to make the time to use my single-step circuit to step my membership card through it's cycle using the following program:

$00 OUT5 $FF
$02 OUT5 $00
$04 BR $00

- P. Todd

This page and edited content is copyright Herb Johnson (c) 2010. Contents written by Lee Hart, are copyright Lee Hart (c) 2010. Copyright of other contents beyond brief quotes, is held by those authors. Contact Herb at www.retrotechnology.com, an email address is available on that page..