Decade Counter (IC 7490) - Computer Programming

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## Wednesday, October 12, 2011

Decade Counter (IC 7490)

AIM:  To verify the truth tables of decade counter IC 7490.

APPARATUS REQUIRED:
1.      Decade Counter trainer kit
2.      Regulated power supply
3.      Connecting wires.
4.      Patch cords.
Theory:
IC 7490 is a decade counter which drives input by 10 and provides BCD outputs 0 to 9, this is also called as decimal counter.  This counter comprises of a divide-by 2 and divide-by 5 counters.  To use as decade counter we have to cascade divide-by 2 and divide-by 5.  Outputs Q0 to Q3 are BCD outputs, inputs A and B are clock inputs to the, divide-by 2 and divide-by 5 counters respectively.  R01 and R02 are the reset inputs, when these are activated counter output goes to 0000.  S91 and S92 are the set inputs to the counter, when these inputs are activated counter output goes to 1001.

Pin diagram and truth tables:

Truth table 1:

Truth table 2:

Procedure:
1. Connect
1. Connect the trainer to the mains and switch on the power supply, measure th output of the regulated power supply, that is, + 5V.
2. Observe the outputs of clock generator and pulse circuit using CRO.
3. Connect R01, R02, S91 and S92 to logic 0.
4. Connect pulser output to A input and short B input and Q0 output.
5. Verify the counter outputs as per truth table 1.

1. Now connect counter outputs to the seven segment display to observe counter output in decimal reading.
2. Repeat the steps 4 to 6 while replacing manual pulse with 1Hz clock.
3. Verify the operations of R01, R02, S91, and S92 according to the truth table 2.

Result: