4-bit Shift Register Animation

In the animation, we start by resetting the flip-flops. Since they all connect to a single control line, a single high pulse is all that is required to reset them simultaneously.

Let us assume that we need to load the 4-bit register with binary 0 0 0 1. Then we should feed binary 1 on the first leading edge of the clock pulse, binary 0 on the second leading edge, binary 0 on the third leading edge, and finally binary 0 on the fourth leading edge.

The animation begins by introducing logic 1 at the serial input, however, at this point, the clock pulse is on the falling edge and nothing happens until the leading edge of the next clock pulse. The leading edge is in red and the falling edge (or trailing edge) in blue.

Keep your eyes on the clock pulses and the logic 1 at the output. You should see that on the leading edge of every clock pulse the logic 1 state moves through successive stages. However, on the falling edge, the state remains locked and nothing happens.