I done a sequence recognizer for the string 1001 with FF JK The equations are: J1 = X' Q0 K1 = X + Q0 J0 = X + Q1 K0 = X' Z = Q1 Q0 X Now I have to simulate it with LTspice, but it doesn't work. The output of the FFs is always 0. Can you help me? I simulated the circuit with an other logic simulator and it works, i don't know if I set some wrong value. Thank you.