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Johnson Ring Counter Circuit with 74LS164

2018-02-28 16:23  
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Counters have numerous application in Digital field. There are many types of counters, today we are going to explain about Johnson counter. Johnson counter is also called as Inverse feedback counter or twisted Ring counter. It has 2N states where ‘N’ is the number of flip-flops. So here is how to make a Johnson counter using IC 74LS164.

Here are some of the features of IC 74164:

Gated (enable/disable) serial inputsFully buffered clock and serial inputsAsynchronous clearTypical clock frequency 36 MHzTypical power dissipation 80 mW

Circuit diagram for Johnson counter using IC 74164 is given below:

Johnson counter

The components needed for this circuit is:

74164 IC7404 IC ? ( Inverter )35Mhz clock source5v supplyIndicators to indicate the state

In above diagram X1 to X8 are indicators to indicate the current state. The 74LS164 IC have 8 flip-flops built-in. So the number of states will be 2 x 8 = 16 states. ?Below diagram shows the truth table which have 16 states.

Truth table

As you can see that there is only one bit change from one state to another state. Every bit starting from X1 goes high after one state till X8. After X8 is high the X1 bit will go low ( 0 ). This is because in the circuit the output of X8 is given as the input to the NOT gate 7404 IC. And the output which is inverted is given back as an input to IC 74164. Hence Johnson counter is also called asInverse feedback counter.

If you have any doubt in the circuit please leave a comment we will respond you.:)

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