## Q4: Maximum Frequency

Q- Find the maximum clock frequency of the following circuit and specifications of the flip-flop are as T (setup) = 5ns T (hold time) = 4ns T (CLK to Q) = 9ns and delay of other components is T (buf) = 2ns,ï¿½ ï¿½  T (AND) = 4 ns, T (OR) = 4 ns,ï¿½ ï¿½ ï¿½ ï¿½  T (NOT) = […]

## 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 & […]

## 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              […]

## Counter other than MOD-2n

Q-Can we design a ripple counter other than MOD-2n? Ans: Yes we can. For this we’ll first design the counter with value which is multiple of 2 but greater than the count required. Then we use a combinational circuit to reset the counter after the required value of count is achieved. Let’s take an example: Design […]

## Ripple counter

We can attach more flip-flops to make larger counter. We just use more flip-flops in cascade and give output of first to the clock of 2nd and output of 2nd to clock of 3rd and so on. This way every flip-flop would divide frequency of the clock by 2 and hence we can obtain a divide by larger […]

## Asynchronous Counters: MOD-2 counter

If we see that flip-flop is a mod-2 counter with starting count as 0. If we connect J & K to HIGH and supply clock to the flip-flop, we’ll see that flip-flop would count pulses 0, then 1 and as it is a MOD-2 counter so it’ll reset and again count from 0.  And the […]

## Johnson Counter

While Ring counter, we have connected Q of last to D of 1st FF, but in Johnson Counter we connect Q bar of last to D of 1st FF as shown below and we also don’t need to connect preset of 1st FF. This is also called Twisted Ring counter: And JK implementation is as follow: And we have […]