Counters:
1. Ripple Counters
A ripple counter is an asynchronous counter where only the first flip-flop is clocked by an external clock. All subsequent flip-flops are clocked by the output of the preceding flip-flop. Asynchronous counters are also called ripple-counters because of the way the clock pulse ripples it way through the flip-flops.
2. Synchronous counters
Synchronous counter – all state bits change under control of a single clock
(or)
The C inputs of all flip-flops receive the common clock pulses
In synchronous counters, the clock inputs of all the flip-flops are connected together and are triggered by the input pulses. Thus, all the flip-flops change state simultaneously (in parallel).
E.g.:-Binary counter
Up-down Binary counter
BCD Binary counter
Ring counter
Johnson counter
Download: Counters Notes
- Counters are sequential circuits that cycle through some states.
- They can be implemented using flip-flops.
- Implementation is simple: using T flipflops (with toggle output) or with any other flip-flops that can be connected to give the required function.
- Ripple(Asynchronous) Counters.
- Synchronous Counters.
A ripple counter is an asynchronous counter where only the first flip-flop is clocked by an external clock. All subsequent flip-flops are clocked by the output of the preceding flip-flop. Asynchronous counters are also called ripple-counters because of the way the clock pulse ripples it way through the flip-flops.
Asynchronous (ripple) counter – changing state bits are used as clocks to subsequent state flip-flops. The flip-flop output transition serves as a source for triggering other flip-flops i.e the C input of some or all flip-flops are triggered NOT by the common clock pulses
Eg:- Binary ripple counters
BCD ripple counters
2. Synchronous counters
Synchronous counter – all state bits change under control of a single clock
(or)
The C inputs of all flip-flops receive the common clock pulses
In synchronous counters, the clock inputs of all the flip-flops are connected together and are triggered by the input pulses. Thus, all the flip-flops change state simultaneously (in parallel).
Up-down Binary counter
BCD Binary counter
Ring counter
Johnson counter