cant count down, dosent start from 9,8,7,6

Thread Starter

mustard ketchup

Joined Apr 6, 2022
i want to count 1,2,3,4,5,6,7,8,9,10,11,12........ and then use the switching circuit (most left with the inverter) to count down. but it doesn't count down from 10, 9, 8, 7, 6 . Left 7 segment displays tens, right 7 segment displays ones.

how do I make count down start from 9 instead of 0? help pls. thank u, load this circuit to simulate, pressing switch enables count down....



Joined Mar 30, 2015
Welcome to AAC!

I don't use Falstad. Could you post a schematic? If Falstad supports print to PDF, kindly post a black and white schematic; preferably without all of those animation artifacts.

Is this counter synchronous? You want to count 1,2,...12, but start counting down from a different number?


Joined Mar 30, 2015
heres a pdf
It's still unreadable.

This is a 3 bit up/down counter I designed. The style I use is a combination of that used by Texas Instruments, Motorola, and RCA:
No vendors label the gate expressions; I do it so I and others can follow the logic (in case there are mistakes that need to be debugged).

EDIT: Here's an asynchronous design example: Not relevant
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