All Your Sequence Belong to Us!

A project log for WITCH-E Decimal Based Computer

Document and create a modern replica of the Harwell Dekatron computer known as the WITCH

Dave's Dev LabDave's Dev Lab 09/15/2017 at 02:271 Comment

After a bit of hiatus on the project, I started back on the next phase of the project which is to expand the input system. Currently I have some test boards to select the "Send" and "Receive" locations as well as selecting the actual function to be executed. This will be replaced with a keypad and eventually also a  "Paper Tape Reader". The input sequence consists of entering 5 digits via the keypad, and then pressing the execute button. I have a 4017 decade counter that steps through each one of the inputs and then kicks off the calculation sequence. The first version of the board was design almost in a "vacuum" as I really didn't have an mental picture of how I was going to connect all of the signals to the board or where the board would physically fit into the system, I was mainly concerned with replicating the original functionality in the WITCH. After assembling the prototype and doing some debugging, I realized that the reset on the D Flip-Flops was an active low while the reset on the 4017 was an active high! DOH! After scabbing on an inverter the design worked as expected. I spent some more time looking at exactly how I would be routing the cables and made some connector changes for the next revision which just arrived and is ready for assembly!


BigEd wrote 09/15/2017 at 14:46 point

Good to see you back!

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