ES210, Digital Design Lab
Reporter Name:
Date:
Partner Names
Group No.:
Lab 10: Ripple Counter *
A. Objectives
 Examine the Ripple Counter and its operation using flip-flops
 Learn how the Ripple Counter can count decimal digits.
 Practice reading the IC datasheets of the logical gates and other ICs for designing digital systems.
B. Introduction
A binary counter is a digital circuit that counts the number of pulses applied to its input. An n-bit binary counter consists
of n flip‐ flops and can count in binary from 0 through 2^n - 1. In a ripple counter the output of each flip-flop is connected
to the input of the next higher order. The flip-flop holding the least significant bit (LSB) receives the incoming count
pulses. A complementing flip‐ flop can be obtained from a JK flip‐ flop with the J and K inputs tied together or a T
flip‐ flop (see sections 5.4 and 6.3 of textbook by Mano). The truth table of JK and T flip-flops are shown below. Clk or
CK are the clock pulses applied to the flip-flop to count up. Q(t) and Q’(t+1) are the current and the next states of the flipflop.
J
K
Q(t+1)
Note
0
0
Q(t)
No Change
0
1
0
Reset
1
0
1
Set
1
1
Q’(t)
Complement
T
Q(t+1)
Note
0
Q(t)
No Change
1
Q’(t)
Complement
The triangle at clock input means trigger by positive edge of the clock, and with a bubble for negative edge. In this
experiment, we want to build first a 2-bit binary counter followed by a BCD ripple counter that counts and displays 0-9.
C. Parts needed

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A Digital Multimeter
A +5 V power supply
A breadboard/protoboard and wires
One 74LS47 BCD-to-7-segment decoders/drivers
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One 74LS76 Dual JK-type flip-flops gates
One 74LS90 Binary and decade counter
One 7730/MAN72
Datasheets of ICs from dept. website or the Internet
D. Procedure (Each member should build the circuits, do the experiment and submit her/his complete report
separately.)
1. Design a 2-bit binary counter similar to Fig. 6.8a in Mano textbook to count binary numbers from Q1Q0=00 to
Q1Q0=11 using T flip-flops (7476 IC). Let the instructor initial the diagram in your logbook before you connect
the circuit. Please use 74LS76 datasheet and Mano Fig 9.12 to answer the questions below for 74LS76.
c. Diagram of a 2-bit binary Counter
a. How many flip-flops are required?
2 flip-flops
b. What are the binary numbers?
00, 01, 10, 11
d. How do you make a T-FF from a JK-FF?
e. What is 74LS76 and what does it do?
f. What are the min, max, and typical Vcc voltages?
Dr. Ali Kujoory
6/30/2016
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g. What is the meaning and value of Input High
voltage?
h. What is the meaning and value of Input Low
voltage?
i. What is the meaning and typical value of Output
High voltage?
j. What is the meaning and typical value of Output
Low voltage?
k. What are the pin numbers for J and K inputs in each
FF?
l. What is the pin number for Load/Preset inputs in
each FF.
m. To toggle what should be the status of Load/Preset
input?
n. What is the pin number for the Clear input in each
FF.
o. To clear what should be the status of the Clear
input?
p. What is the pin number for the Clock input in each
FF.
q. Is this FF triggered on the positive or negative edge
of the clock pulses?
r. What is the Maximum Clock Frequency of this IC?
2.
Connect the 2-bit binary counter on the protoboard. Set T=J=K= high logic. Connect a LED (LED1) to a switch (or a
push button) to see the status of the switch. Use the switch to apply pulses to the clock input of the first stage with Q0
output (LSB) connected to LED2 and the second stage with Q1 (MSB) connected to LED3 to display the output bits.
For the flip-flops to toggle, set the Preset and Clear inputs of both flip-flips to high logic (Mano Fig 9.12).
Complete the table below for the counter by applying the clock pulses to the first stage and watching the LEDs. Let
the instructor check and initial the diagram in your logbook. Complete the table below.
ON/OFF Counts (LED1)
1
2
3
4
Q0
LED2
Q1
LED3
3. In your logbook, design and draw a circuit to count and display from decimal 0 to 9 using a 74LS90 BCD ripple
counter, a 74LS47 BCD-to-7-segment decoder/driver, and a 7730 (or MAN72) 7-segment display IC as shown below.
Use a switch or push buttons to mimic the input pulses and connect it to an LED to display the switch status. Also
include a switch to reset the counter to zero. Include all pin numbers and their connections on the three ICs.
The input at pin 14 of 7730/Man72 is the common anode (CA) for all the LED segments. A 47Ω resistor to Vcc is
needed in order to supply the proper current to the selected LED segments.
Answer the following question. Let the instructor check the circuit before connecting it on the breadboard.
Input
pulses
74LS47
BCD-to-7-segment
decoders/drivers
74LS90
BCD Counter
Question
7730/MAN72
7-Segment
display
Answer
a. What is 74LS90 IC and what does it
do?
b. How many flip-flops are in 7490 IC?
Dr. Ali Kujoory
6/30/2016
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c. How many outputs does 7490 have
for the BCD digits.
d. Which output of 7490 is LSB and
which one is MSB?
e. What is 7447 IC and what does it do?
f. How many inputs does 7447 have for
the BCD digits?
g. How many outputs does 7447 have
for the BCD digits?
h. How many LEDs does 7730 /
MAN70A have for the BCD digits?
i. Which segments are used to display
digit 0?
j. Which segments are used to display
digit 4?
k. Which segments are used to display
digit 9?
3. Using the above diagram, start with the 7490 IC, connect and test each IC on the protoboard separately before
connecting it to the next stage. Use the truth table of 7490 to check your wiring for the reset inputs. You can connect
the 4 outputs of 7490 to the LEDs on the protoboard to check the counting. Also check the reset switch operation.
Let the instructor check and initial your logbook and that the circuit is operating as required.
a. What needs to happen for a binary
counter to operate as a BCD counter?
Does the 7-segment IC display digits from 0 to 9 as you push the switch/button 10 times?
Does the 7-segment IC reset to zero as you hit the reset switch?
4. Next, set the switch on the waveform generator on the protoboard to TTL and the frequency to 1 Hz, connect the signal
to the BCD counter, and read the 7-segment display. Let the instructor check and initial your logbook for this.
Does the 7-segment IC display show digits 0 to 9 back to 0 to 9 continuously?
Do not disassemble the circuit from your breadboard since you may need it for the next experiment.
E. Feedback/Comments (your comments will help improving this lab)
Was the instruction clear enough? Any error?
How difficult was it for you?
Do you have any observations to make?
F. Report
1. Report the answers in the tables above. You do not need to include the unnecessary text such as the objectives,
instructions, and procedures in the report.
2. Each member should submit her/his complete report separately.
(*) The author acknowledges Mr. S. Marivani and as some of the sections come from his work.
Dr. Ali Kujoory
6/30/2016
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