Synchronous Counters

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Synchronous Counters
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Lecture Overview

• Classifications of Counters
• Definitions
• Synchronous Counter
• Modulus 8 with Discrete Gates (SSI)
• Modulus 16 with Discrete Gates (SSI)
• 74LS163 Synchronous 4 Bit Counter
• Understanding Device
• Truncated Count

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Classifications of Counters

• Asynchronous Counters
• 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 slower than synchronous
  counters because of the delay in the transmission
  of the pulses from flip-flop to flip-flop.
• Asynchronous counters are also called
  ripple-counters because of the way the clock
  pulse ripples it way through the flip-flops.
• Synchronous Counters
• All flip-flops are simultaneously clocked by an
  external clock.
• Synchronous counters are faster than asynchronous
  counters because of the simultaneous clocking.
• Synchronous counters are an example of a state
  machines design.

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Modulus-8 Synch Counter Analyses

• Q0 Toggles Every Time J0 K0 1
• Q1 Toggles When Q01 J1 K1 Q0
• Q2 Toggles When Q01 Q11 J2 K2 Q1 x Q0

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Modulus-8 Synch Counter Design
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Modulus-16 Synch Counter Analyses

• Q0 Toggles Every Time J0 K0 1
• Q1 Toggles When Q01 J1 K1 Q0
• Q2 Toggles When Q01 Q11 J2 K2 Q1 x Q0
• Q3 Toggles When Q01 Q11 Q21 J3 K3
  Q2xQ1xQ0

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Modulus-16 Synch Counter Design
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74LS163 Synchronous 4 Bit Counter
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74LS163 How It Works
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74LS163 6 (0110) to 15 (1111) CNT
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74LS163 6 (0110) to 12 (1100) CNT
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Understanding Circuit Maker Labels
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