error in schematic

[phiber1]

Hello Matt, I happened to notice an error in your schematic. Specifically U17, the second decoder in the 74139 being used to do the chip-select read and chip-select write on the VDP... Your decoding of A and B to Y1 and Y2 is backwards. If you consult the truth table, \A -> \Y2, and \B -> \Y1. So you either need to reverse your schematic wiring of \WR and \RD at the inputs, or otherwise reverse \CSW and \CSR at the outputs. Either or. Otherwise the VDP obviously won't work at all.

Regards,
Mark

[74hc595]

This is a known error and is documented here: https://github.com/74hc595/Ultim809/blob/master/circuit/board-rev0%20(has%20errors)/rev0-errors.txt

Sorry it has taken an eternity for me to respond! This project has been on the shelf for a while. I'd love to do a second revision of the Ultim809 and fix the errors one of these days.

[phiber1]

So it is! I've never actually built your system, but I created my own 63C09 homebrew some years back which runs FLEX and CUBIX OSes. I have a different sound chip in mine, but I did adapt your Asteroids game to run on my system, adjusting for the sounds. I also corrected the "OUT OF OBJECTS!" error for those of us that actually play well and go on for a while. :) Well done.

…

-Mark

On Fri, Sep 21, 2018 at 12:12 PM, Matt Sarnoff ***@***.***> wrote: This is a known error and is documented here: https://github.com/74hc595/ Ultim809/blob/master/circuit/board-rev0%20(has%20errors)/rev0-errors.txt Sorry it has taken an eternity for me to respond! This project has been on the shelf for a while. I'd love to do a second revision of the Ultim809 and fix the errors one of these days. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#2 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AMEKmGBqXmVOcPD1ZR1GQ_gwhKsDlMs0ks5udToSgaJpZM4EuT5Y> .