258 State machine of an impulse counter

258 : State machine of an impulse counter

How it works

By clocking the state machine adress pins a2, a1 and a0 change their values every 12 clocks. Shift/load pin is set to 1 and then back to zero every 12 clocks. Other outputs are used for debugging.

How to test

After an impulse on reset pin and a subsequent impulse on the ovf pin, you can start clocking the circuit. Adress pins marked with “a” should follow the sequence: “100”->“000”->“001”->“010”->“011”->“000”. Shift/load pin wil be set to 1 after every adress change and then set back to 0 on the next clock. The sequence will repeat itself.


# Input Output Bidirectional
0 reset counter flop1 a2
1 ovf counter flop2 a1
2 clk counter flop3 a0
3 bi oe counter flop4 shift/load
4 none zero sm flop1
5 none one sm flop 2
6 none global reset sm flop 3
7 none ovf sm flop 4