10a 3 Bit Up Down Counter Done

Digital Electronics Lab (Pattern 2015)
Assignment No: 10(A) Group B

R C O T Dated
(2) (4) (2) (2) Sign
 Title: Synchronous counter

 Objective: 3 Bit up/down synchronous Counter
 Problem Statement: To design and implement 3 bit UP and Down, Controlled
UP/Down Synchronous Counter using MS-JK Flip-flop.
 Hardware & Software Requirement’s :
Digital Trainer Kit, IC 7476, IC 7408, IC 7432 & IC 7404.patch cords, +5V power
supply.
Theory:
Counters: counters are logical device or registers capable of counting the no of states
or no of clock pulse arriving at its clock input where clock is a timing parameter
arriving at regular intervals of time, so counters can be also used to measure time &
frequencies. They are made up of flip flops. Where the pulse are counted to be made of it
goes up step by step & the o/p of counter in the flip flop is decoded to read the count to
its starting step after counting n pulse incase of module & counters.
 Synchronous Counter:
In this counter, all the flip flops receive the external clock pulse
simultaneously.
Ex:- Ring counter & Johnson counter
The gates propagation delay at reset time will not be present or we may
say will not occur.
 Classification of synchronous counter:
Depending on the way in which counting processes, the synchronous

counter is classified is :-
1) Up counter.
2) Down counter.
3) Up down counter.
1
S.N.J.B.’s College of Engineering, Chandwad
 Up Counter:
The up counter counts binary form 0 to7 i.e.(000 to 111).It counts from
small to large number. It’s O/P goes on increasing as they receive clock pulse
 Down Counter:
This down counter counts binary from 7-0 i.e.(111-000).It counts from
large to small number. It’s O/P goes on increasing as they receive clock pulse
 Excitation Table:- The tabular representation of the operation of flip flop (i.e:
Operational Characteristic)
Present State Next State J K

0 0 0 X
0 1 1 X
1 0 X 1
1 1 X 0
For M = 0, it acts as an Up counter and for M =1 as an Down counter.
State Table for 3 bit Up-Down Synchronous Counter:
Control Present State Next State Input for Flip-flop

input M QC QB QA QC+1 QB+1 QA+1 JC KC JB KB JA KA
0 0 0 0 0 0 1 0 X 0 X 1 X
0 0 0 1 0 1 0 0 X 1 X X 1
0 0 1 0 0 1 1 0 X X 0 1 X
0 0 1 1 1 0 0 1 X X 1 X 1
0 1 0 0 1 0 1 X 0 0 X 1 X
0 1 0 1 1 1 0 X 0 1 X X 1
0 1 1 0 1 1 1 X 0 X 0 1 X
0 1 1 1 0 0 0 X 1 X 1 X 1
1 0 0 0 1 1 1 1 X 1 X X 1
1 0 0 1 0 0 0 0 X 0 X 1 X
1 0 1 0 0 0 1 0 X X 1 X 1
1 0 1 1 0 1 0 0 X X 0 1 X
1 1 0 0 0 1 1 X 1 1 X X 1
1 1 0 1 1 0 0 X 0 0 X 1 X
1 1 1 0 1 0 1 X 0 X 1 X 1
1 1 1 1 1 1 0 X 0 X 0 1 X
2
K- map Simplification:
QBQA 00 01 11 10
MQC
00 X 1 1 X
01 X 1 1 X
11 X 1 1 X
10 X 1 1 X
JA = 1 KA = 1
QBQA 00 01 11 10 QBQA
MQC MQC 00 01 11 10
00 0 1 X X 00 X X 1 0
01 0 1 X X 01 X X 1 0
11 1 0 X X 11 X X 0 1
10 1 0 X X 10 X X 0 1
JB = M QA + M QA KB = M QA + M QA
QBQA QBQA
00 01 11 10 MQC
00 01 11 10
MQC
00 0 0 1 0 00 X X X X
01 X X X X 01 0 0 1 0
11 X X X X 11 1 0 0 0
10 1 X 0 0 10 X X X X
JC = M QA QB + M QA QB KC = M QA QB + M QA QB
3
PR
VCC
J QA J QB J QC
K QA K QB K QC
CLR
M
CLK
QA QB QC
Fig : Logical Diagram of Up down counter using JK Flip Flop
Uses:
2) The synchronous counter is specially used as the counting devices.
3) They are also used as counter to count the no of clock pulses applied.
4) It also works for counting frequency & is used in frequency divider circuit.
5) It is used in digital voltmeter.
6) It is also used in counter type A to D converter.
7) It is also used for time measurement.
8) It is also used in digital triangular wave generator.
9) It helps in counting the no of product coming out from machinery where product is
coming out at equal interval of time.
Outcome:
Up and down counters are successfully implemented, the counters are studied
& o/p are checked. The truth table is verified.
Enhancements/modifications:
As the design part is done for the 3 bit Counter, we can implement the same for 4 bit
counter.
Assignments Questions:
FAQ’s with answers:
4
 What do you mean by Counter?

A Counter is a register capable of counting the no. of clock pulses arriving at its
clock inputs. Count represents the no. of clock pulses arrived. A specified sequence
of states appears as the counter output.
 What are the types of Counters? Explain each.
There are two types of counters as Asynchronous Counter and Synchronous Counter.
Asynchronous Counter: In this counter, the first flip-flop is clocked by the external
clock pulse and then each successive flip-flop is clocked by the Q or Q’ o/p of the
previous flip-flop. Hence in Asynchronous Counter flip-flops are not clocked
simultaneously and hence called as Ripple Counter.
Synchronous Counter: In this counter, the common clock input is connected to all
the flip-flops simultaneously.
 What do you mean by pre-settable counters?
A counter in which starting state is not zero can be designed by making use of the
preset inputs of the flip flops. This is referred to as loading the counter
asynchronously.
This is referred to as pre-settable counter.
 What are the applications of synchronous counters?
Digital clock
Frequency divider circuits
Frequency counters
Used in analog to digital converters
 What are the advantages of synchronous counters over asynchronous counters?
Propagation delay time is reduced
Can operate at a much higher frequency than the asynchronous counters.
 Ring counter is an example of synchronous counters or asynchronous counter?
Synchronous counter. Since all the flip flops are clocked simultaneously.
 Twisted Ring (Johnson’s) counter is an example of synchronous counters or
asynchronous counter?
Synchronous counter. Since all the flip flops are clocked simultaneously.
 What is the difference between ring counter and twisted ring counter?
5
In ring counter pulses to be counted are applied to a counter , it goes from state to
state and the output of the flip flop s in the counter is decoded to read the count. Here
the uncomplimentary output (Q) of last flip flop is fed back as an input to first flip
flop. Ring counters are referred as MOD ‘N’ counters.
But in Twisted ring counter the complimentary output (Q bar) of last flip flop is fed
back as an input to first flip flop. Twisted Ring counters are referred as MOD ‘2N’
counters.
 What are the applications of ring counters?
Ring counter outputs are sequential non-overlapping pulses which are useful for
control state counters,
Used in stepper motor, which requires pulses to rotate it from one position to the next.
Used as divide by ‘N’ ((MOD ‘N’) counters.
 What are the applications of ring counter twisted ring counters?
Used as divide by ‘2N’ ((MOD ‘2N’) counters.
Used for control state counters.
Used for generation of multiphase clock.
 List the Synchronous Counter ICs.
IC 74160 : Decade Up Counter
IC 74161 : 4 bit binary Up Counter
IC 74162 : Decade Up Counter
IC 74163 : 4 bit binary Up Counter
IC 74168 : Decade Up/Down Counter
IC 74169 : 4 bit Binary Up/Down Counter
6

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Digital Electronics Lab (Pattern 2015)

Assignment No: 10(A) Group B

 Title: Synchronous counter

Ex:- Ring counter & Johnson counter

 Classification of synchronous counter:

Depending on the way in which counting processes, the synchronous

Present State Next State J K

For M = 0, it acts as an Up counter and for M =1 as an Down counter.

State Table for 3 bit Up-Down Synchronous Counter:

Control Present State Next State Input for Flip-flop

Fig : Logical Diagram of Up down counter using JK Flip Flop

FAQ’s with answers:

 What do you mean by Counter?

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