'Why Asynchronous Counter are named as Ripple Counter, Explain.?

Question

'Why Asynchronous Counter are named as Ripple Counter, Explain.

Answer 1

Dear Muhammad,
Ripples spread out from a stone thrown into a pond.
In a deep pond they spread as circles.
In a pond of varying depth their shape distorts due to changes in depth or toplogy of the surface.

A counter has many stages of Flip-Flops which are activated in turn by previous stages. The signal seems to pass through the counter like a wave.
In a synchronous counter the subsequent stages can only change states when the clock pulse ticks. This process is called ticking over. It is a well controlled process.

In the asynchronous counter each stage changes state in its own time, depending on inductances etc in the connecting wires. This process is called rippling. If the signal separates and rejoins later we get a race condition or contention - so when we design the circuit we must make sure that the various propogation delays do not give rise to 'glitches' which may cause random triggering in subsequent circuits.

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