This presentation is all about counters, focusing on asynchronous and synchronous counters. The unique feature is the incorporation of the circuit images generated from MULTI SIM software imparting practical knowledge to the users.

1. COUNTERS
SYNCHRONOUS & ASYNCHRONOUS
Presentation by:
C.MURALIDHARAN
V.A.SAIRAM
A.SUBHA SHREE

2. COUNTER
• The Counter is an electronic circuit that counts the events. The
events can be numbers.
• It can also count the event related to the clock like rising
edge(low to high) and trailing edge(high to low)
• It is a type of sequential logic circuit i.e. The present output
depends on the present input and the combination of previous
input)
• Counter can be designed using t-flipflop(which is a special case
of JK flipflop).

3. TYPES OF COUNTERS
• Broadly counters can be classified into two types based on the modes
of operation.
• Synchronous
• Asynchronous
• In Synchronous mode, all the flip-flops receive input at the same
time and produce output at the same time. Synchronous counters are
counters that use the clock signal at the same time.
• In Asynchronous mode, the clock is given only to the first flip flop
and each flipflop produces output one at a time. The input for the
successive flip-flops depends on the previous ones. These counters
are also called “RIPPLE COUNTERS”.
• These counters can again be categorized as UP and DOWN counters.

4. WHY SYNCHRONOUS COUNTERS?
• The major drawback in asynchronous counters is that they are
limited to high frequencies due to the propagation delay.
• Synchronous counters can be operated at higher frequencies.
• Synchronous counters are faster in operation.
• Easy to design.
• No delay in synchronous counters.

5. TABLE OF CONTENTS
• MOD 4 Asynchronous
• MOD 4 Synchronous
• MOD 7 Asynchronous
• Specialized IC for Counters
• MOD 8 Asynchronous
• MOD 8 Synchronous
• MOD 16 Asynchronous
• MOD 16 Synchronous
• Applications of Counter

6. MOD 4 ASYNCHRONOUS
• MOD (fully known as modulus) is
nothing but the number of output
states of the counter.
• MOD 4 will have 4 output states
produced in asynchronous manner.
• Now, the number of flip flops(i.e. n)
is based on the given formula:
• 2𝑛 = MOD
• Here we already know that the
output state is 4. So 2𝑛
=4 implies
n=2.
• 2 flip flops are used to produce the
4 counts in MOD 4 asynchronous
counter.
• 4 output states are nothing but

7. O/P-1(01) O/P-
2(10)
These are some of the outputs of MOD 4 asynchronous counters. Q0 is LSB(Least
Significant Bit) and
Q1 is MSB (Most Significant Bit).
 The first figure represents output 1 with Q1=0 & Q0=1 i.e. 01(Binary for 1)
 The second figure represents output 2 with Q1=1 & Q0=0 i.e. 10(Binary for
2) O/P-output

8. MOD 4 SYNCHRONOUS
• This is MOD 4 synchronous counter
where the count happens in two ways as
follows: ascending (UP) or in descending
manner (DOWN).
• These counters are easier than
asynchronous counters.
• Like the previous one,2 flip flops are
needed to produce the 4 output states.
The difference is that in synchronous
counters, the output changes
simultaneously due to the common
clock pulse and the count is done
sequentially in synchronous counter.
• Here the counter counts from 0 to 3 (00

9. O/P-2(10) O/P-3(11)
Here are some of the outputs of the MOD 4 synchronous counter with the same
Q0 as LSB and Q1 as MSB
 The first figure represents output 2(10 in binary)
 The second figure represents output 3(11 in binary)

10. MOD 7 ASYNCHRONOUS
• From the title, we came to know that
the output state is 7.
• We know to calculate the number of
flip flops from the formula =output
state (7)
• Here 7 is not a multiple of 2, hence we
may get confused about how to choose
the number of flip flops when the
output state is not equal to 2𝑛
• In that case we choose a number which is a
multiple of 2, greater and nearer to 7. the
number that satisfies all the above
conditions is 8(23
). Hence, we conclude that
we should choose the least possible number
of flip-flops.
• It is not fully sequenced. These types
of counters are called truncated
counters.
• All the outputs of the flipflop are
2𝑛

11. • Here we consider MOD 7 as an example.
• After count 6, it automatically tries to go to count 7 (111 in binary) which is not
required here.
• In that case the value 1 of all the flip-flops moves to the NAND gate.
• So the output is 0 which is again sent to the clear pins of the respective flip
flops that use a NAND gate to reset to the required count between 0 to 5.
• A Clear pin is a special pin present in T flip-flop (special of JK flip-flop). Once it
is activated it resets the flip flop(0) irrespective of a past condition. The clear pin
is activated by a logic low (0) signal. In this case, all the flip flop gets reset and
the value goes to 0. Hence MOD 7 is achieved.
• This gave the way for the IC 74293 that is embedded with 4 flip flops and a
NAND gate.
• NAND gate is mainly used to detect the output 1 which is generated by the flip-
flops.
WORKING OF THE TRUNCATED COUNTERS

12. O/P-4 O/P-5
 The output 4(100 in binary) and output 5(101 in binary) of MOD 7
asynchronous counter is represented here.

13. MOD 8 ASYNCHRONOUS
• MOD 8 Asynchronous counter can
be designed using 3 flip-flops.
• It is a fully sequenced counter.
• 2𝑛
=8 implies n=3
• It counts from 000 to 111 i.e. 0 to
7

14. O/P-2 O/P-6
LSB is Q0 and MSB is Q2
 The first figure represents output 2(010 in binary)
 The second figure represents output 6(110 in
binary)

15. MOD 8 SYNCHRONOUS
• MOD 8 synchronous counter is
designed using 3 flip flops.
• It is also a fully sequenced counter
which counts in a sequential
manner from 0 to 7 or 7 to 0.
• The second flipflop gets its input
from the output of first flipflop
(Q1), the third flipflop gets its
input from the outputs of the first
and second flipflop through a AND
gate.

16. O/P-5 O/P-7
 The output 5(101 in binary) and output 7(111 in binary) of MOD 8 synchronous
counter is given here.

17. MOD 16 ASYNCHRONOUS
• MOD 16 asynchronous counter is
designed using 4 flip-flops as per the
formula.
• It counts from 0000 to 1111 i.e. 0 to F(in
hexadecimal)
• The outputs of all the four flip-flops are
connected to a four-pin NAND gate
• Its output is sent to the clear pins of all
the flip-flops.
• The counter has to reset back to 0(0000)
after counting 15(1111).
• In the case of 15, the NAND gate receives
1 in all inputs, it produces an output of 0.
• This logic 0 activates the clear pin of all
flipflops resetting them to count 0.

18. O/P-13 O/P-14
Here Q1 is LSB and Q4 is MSB
 The first picture represents output 13 (decimal value) i.e.1101 in binary. It
is converted into hexadecimal value as ‘d’ and displayed.
 Similarly the next output 14 i.e. 1110 in binary is displayed as ‘E’
(Hexadecimal value).

19. MOD 16 SYNCHRONOUS
• MOD 16 synchronous counter can be
constructed using 4 flipflops.
• It can do either up count operation
(0-15) or down count operation (15-
0).
• The second flipflop gets its input
from the output of first flipflop (Q1),
the third flipflop gets its input from
the outputs of the first and second
flipflop through a AND gate.
• The fourth flipflop receives its input
from the output of first, second and
third flipflops.
• A trick is to use the output of the
previous flipflop along with the
output of the previously connected
AND gate.

20. O/P 12 O/P 14
Here again, Q0 is LSB and Q3 is MSB
 The first figure represents output 12 i.e.1100 in binary (“C” in
hexadecimal)
 The second one represents output 14 i.e.1110 in binary (“E” in
hexadecimal)

21. UP-DOWN COUNTERS
• As the name suggests it counts in both
ways i.e. from low to high and also from
high to low.
• So these are also called bidirectional
counters.
• They are built using JK flip-flops.
• Here it is a 4 bit UP-DOWN counter.
• It counts from 0 to F on one side and F
to 0 on the other side.
• These are self reversing and used in
clock divider circuits.

22. COUNTS FOR UP-DOWN COUNTER
 Some of the output counts
of the UP-DOWN counter

23. APPLICATIONS OF COUNTERS
• Frequency counters
• Digital clocks
• Analog to digital converter
• Calculators etc.,

24. 1) C.MURALIDHARAN
Assistant Professor, Biomedical Engineering, Rajalakshmi
Engineering College
2) A.SUBHA SHREE
Student, Biomedical Engineering, Rajalakshmi Engineering
College
3) V.A.SAIRAM
Student, Biomedical Engineering, Rajalakshmi Engineering
College

25. REFERENCES:
• https://www.electronics-tutorials.ws/counter/count_3.html
• https://www.electronicshub.org/synchronous-counter/
• https://www.electronicshub.org/asynchronous-counter/

26. THANK YOU