Multisim and Ultiboard

cancel
Showing results for 
Search instead for 
Did you mean: 

SR Flip-Flop not Flipping?

I'm trying to create a bi-directional counting circuit that toggles an SR flip-flop when the upper number is reached, causing the circuit to count down. Then, when the lower number is reached, it sets the SR Flip-Flop to count back up. When using manual switches in the simulation, it works fine. But when I try to Set or Reset the flip-flop from the output of the counter, it doesn't. Any idea what I'm doing wrong here?
0 Kudos
Message 1 of 2
(3,946 Views)
The "S" input on the FF is unterminated (except when you use the switch) during operation.  I would look into put that input into a known state.  Start with a pull-up to see if it will count up then back down.  If it does, then you can add other logic to the "S" input to have the circuit function the way you want
0 Kudos
Message 2 of 2
(3,936 Views)