SynchronousSynchronous CountersCounters

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

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.

Modulus-8 Synch Counter Analyses

Q0 : Toggles Every Time… J0 & K0 = 1

Q1 : Toggles When Q0=1… J1 & K1 = Q0

Q2 : Toggles When Q0=1 & Q1=1… J2 & K2 = Q1 x Q0

Q2

Q1

Q0

Modulus-8 Synch Counter Design

Modulus-16 Synch Counter Analyses

Q0 : Toggles Every Time… J0 & K0 = 1

Q1 : Toggles When Q0=1… J1 & K1 = Q0

Q2 : Toggles When Q0=1 & Q1=1… J2 & K2 = Q1 x Q0

Q3 : Toggles When Q0=1 & Q1=1 & Q2=1… J3 & K3 = Q2xQ1xQ0

Q3

Q2

Q1

Q0

Modulus-16 Synch Counter Design

Data In Data Out

Terminal CountClear

Load Data

74LS163 Synchronous 4 Bit Counter

Enables

74LS163 : How It Works

74LS163 : 6 (0110) to 15 (1111) CNT

74LS163 : 6 (0110) to 12 (1100) CNT

Understanding Circuit Maker Labels

DATASHEET

CIRCUITMAKER