Skip to main content

Short note: Shift register and counter

Short answer

A shift register is a serial chain of flip-flops shifting data one bit per clock pulse; types include SISO, SIPO, PISO, PIPO. A counter is a sequential circuit that counts clock pulses through a fixed state sequence; asynchronous ripple counters are simple, synchronous counters are faster, used for frequency division and counting.

Write a short note on shift register and counter.

Shift register

A shift register is a group of flip-flops connected in series, so that the stored binary data shifts by one position on every clock pulse. An n-bit register uses n flip-flops (D or JK) and stores n bits.

 Serial   +----+   +----+   +----+   +----+
 in ----->| FF0|-->| FF1|-->| FF2|-->| FF3|--> Serial out
          +----+   +----+   +----+   +----+
             ^        ^        ^        ^
 CLK --------+--------+--------+--------+

Types: SISO (serial-in serial-out), SIPO, PISO, PIPO. Uses: temporary data storage, serial-to-parallel and parallel-to-serial conversion, time delay, and ring or Johnson counters.

Counter

A counter is a sequential circuit made of flip-flops that counts the clock pulses and goes through a fixed sequence of states.

  • Asynchronous (ripple) counter: the output of one flip-flop is the clock of the next; simple but slow.
  • Synchronous counter: all flip-flops receive the same clock; faster.
  • An n-bit counter has a modulus up to 2ⁿ (a 3-bit counter counts 0 to 7). A BCD (decade) counter counts 0 to 9.
  • Up, down, and up/down counters exist.

Uses: frequency division, digital clocks, event counting, timers, frequency meters.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Basic Electronics Engineering chapter 6 questions →