Construct 4 bit ring counter using IC 74194 and draw output waveform

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written 8.4 years ago by

teamques10 ★ 67k

IC 7494 is a 4-bit universal shift register. It has four parallel data inputs and four outputs. It has two control pins $S_0$ and $S_1$ which when connected to high transfer data appearing on input pins on the output pin.
When $S_0S_1$ is 10, shift left is accomplished, in which serial data is entered at the shift left serial input $D_{SL}$.
Consider the circuit shown

enter image description here

The figure above shows the circuit diagram for a 4-bit ring counter with a single circulating 1.
Here IC 7494 universal shift register is connected so that it normally performs a left shift.
However when reset is asserted, it loads 0001.
Once reset is negated the IC 7490 shifts left on every clock pulse. The $D_{SL}$ serial input is connected to the leftmost output (Q3 : MSB), so the next states are 0010, 0100, 1000, 0001, 0010,....
Thus the counter visits four unique states before repeating.
Following is the output waveform:

enter image description here

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