Counters

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Counters

  1. 1. Counters• Counters are a specific type of sequential circuit.• Like registers, the state, or the flip- flop values themselves, serves as the “output.”• The output value increases by one on each clock cycle.• After the largest value, the output “wraps around” back to 0. 1
  2. 2. Using two bits: 1 00 01Present State Next State A B A B 0 0 0 1 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 11 10 2
  3. 3. RIPPLE COUNTER(ASYNCHRONOUS COUNTER) 3
  4. 4. Asynchronous Counters• This counter iscalled asynchronousbecause not all flipflops are hooked tothe same clock. 4
  5. 5. • This is called as a ripple counter due to the way the FFs respond one after another in a kind of rippling effect.• In a ripple counter, a flip-flop output transition serves as a source for triggering other flip- flops. 5
  6. 6. 6
  7. 7. Asynchronous countersIf the clock has period T.Q0 has period 2T. Q1period is 4TWith n flip flops the periodis 2n. 7
  8. 8. • Binary Ripple Counter –(2 bits, 3 bits, 4 bits, …) – 1 to 0• Binary Countdown Counter – 0 to 1• BCD Ripple Counter –4 bits 8
  9. 9. 9
  10. 10. BINARY RIPPLE COUNTER 10
  11. 11. BINARY COUNTDOWN COUNTER 11
  12. 12. 12
  13. 13. BCD RIPPLE COUNTER 13
  14. 14. 14

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