Q- Find the maximum clock frequency of the following circuit if specifications of the different flip-flop are as T1 (setup) = 5ns T1 (hold time) = 4ns T1 (CLK to Q) = 9ns, T2 (setup) = 4ns T2 (hold time) = 3ns T2 (CLK to Q) = 7ns T3 (setup) = 4ns T3 (hold time) […]

## 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 […]

## 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 […]

## Comparison b/w Synchronous & Asynchronous counters

Asynchronous Synchronous Circuit The logic circuit of this type of counters is simple to design and we feed output of one FF to clock of next FF The circuit diagram for type of counter becomes difficult as number of states increase in the counter Propagation Time Propagation time delay of this type of counter […]

## 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 & […]

## 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 […]

## 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 […]

## Down Counter (Reverse counting)

Here we’ll be counting in reverse order i.e. count would start from 15 to 0 and again value goes from 0 to 15. We just make a change in the circuit as we give Q bar to the CLK of next flip-flop or we use positive edged flip-flops and give Q to CLK of next […]

## 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 […]

## 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 […]