Sequential Circuits

Q1: Maximum Frequency

Q- Find the maximum clock frequency of the above circuit if specifications of the flip-flop are as T (setup) = 5ns     T (hold time) = 4ns             T (CLK to Q) = 9ns and maximum delay of the combinational circuit is T (c-delay) = 13 ns. There is a clock skew of +3ns for 2nd FF in […]

Sequential Circuits

Clock Skew

It is a phenomenon in which there is a difference between the times at which clock signal reaches different components in synchronous circuits. Or we can say that clock signal from clock circuitry reaches different components in the circuit at different times. e.g. If in the circuit given below, CLK signal reaches the two flip-flops at […]

Sequential Circuits

Synchronous Counter

In synchronous counters we have the same clock signal to all the flip-flops. MOD-4 Synchronous counter: We discuss here a 2-bit synchronous counter. We have the circuit for this as:s We have the initial outputs as Q0=0 & Q1=0. Whenever the first negative clock edge comes O/P of 1st FF becomes 1 as we have J & […]

Sequential Circuits

Glitch

A glitch is an unwanted pulse which gets generated due to little difference in the delays of signals. Whenever signals with glitches are used as clock then glitches causes unwanted triggering of the flip-flop.  e.g. We can see in the wave-forms given above for MOD-14 counter that there is a glitch in the Q2 signal […]

Sequential Circuits

Q: Design custom ripple counter

Q- Design the ripple counter whose output sequence is represented by the following state diagram. Ans: As we can see that it is a down counter so we’ll be using Q bar of all flip-flops as clock to next flip-flops (negative edged FFs). We draw the table as  Q2         Q1          Q0                          OUTPUT 0              0              0                              0 […]

Sequential Circuits

Q: Design custom ripple counter

Q- Design the ripple counter whose output sequence is represented by the following state diagram. Ans: As it is a 3-bit counter hence we firstly arrange 3 FFs and now we design the combinational circuit to reset the counter at appropriate point.  Q2         Q1          Q0                          OUTPUT 0              0              0                              0 0              0              1                              1 0              1              […]

Sequential Circuits

Q: MOD 6 Counter

Q- Can we design a MOD-6 counter using the above method? Ans:  We firstly draw the state diagram And now we draw the table to represent the desired output of the combinational circuit to reset FFs as: Q2          Q1          Q0                          OUTPUT 0              0              0                              1 0              0              1                              1 0              1              0                              1 0              1              […]