Synchronous Counters
Lecture Overview
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Classifications of Counters
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Definitions
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Synchronous Counter…
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Modulus 8 with Discrete Gates (SSI)
Modulus 16 with Discrete Gates (SSI)
74LS163 Synchronous 4 Bit Counter
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Understanding Device
Truncated Count
Classifications of Counters
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Asynchronous Counters
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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
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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.
Modulus-8 Synch Counter Analyses
Q2
Q1
Q0
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Q0 : Toggles Every Time… J0 & K0 = 1
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Q1 : Toggles When Q0=1… J1 & K1 = Q0
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Q2 : Toggles When Q0=1 & Q1=1… J2 & K2 = Q1 x Q0
Modulus-8 Synch Counter Design
Modulus-16 Synch Counter Analyses
Q3
Q2
Q1
Q0
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Q0 : Toggles Every Time… J0 & K0 = 1
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Q1 : Toggles When Q0=1… J1 & K1 = Q0
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Q2 : Toggles When Q0=1 & Q1=1… J2 & K2 = Q1 x Q0
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Q3 : Toggles When Q0=1 & Q1=1 & Q2=1… J3 & K3 =
Q2xQ1xQ0
Modulus-16 Synch Counter Design
74LS163 Synchronous 4 Bit Counter
Clear
Terminal Count
Data In
Data Out
Enables
Load Data
74LS163 : How It Works
74LS163 : 6 (0110) to 15 (1111) CNT
74LS163 : 6 (0110) to 12 (1100) CNT
Understanding Circuit Maker Labels
DATA
SHEET
CIRCUIT
MAKER