The document presents a project on building a BCD counter. It introduces the group members and provides an overview of the content which includes introduction, background, necessary materials, circuit diagram, pin assignments, working principle and timing diagram of the BCD counter. It discusses how a BCD counter works from generating a clock pulse to displaying the output in decimal on a 7 segment display. It also includes the Xilinx module description and test bench for verification.

1. Project Presentation
Name of the project : BCD Counter
Group 3
 S.M Shahriar Mahmud 021 131 063
 Ahmed Amirul Arefin 021 131 088
 Tariqul Islam 021 131 085
 Israt Jahan 021131113

2. Content
 Introduction of BCD counter
 Background of BCD counter
 BCD counter brief discussion
 Necessary materials
 Circuit /Connection diagram
 Pin assignments of ICS
 Working Principle
 Timing diagram of a IC
 Xilinx module description
 Test bench of the Xilinx module
 Conclusion

3. The digital timer we are going to build is a BCD
counter. Which means it can count 4bit binary 0000
to 1001(decimal 0-9). And then it will start from the
beginning again . Its also called ''8421''code.
BCDCOUNTER
Decimal BCD
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001

4. BCD is very common in electronic systems where a numeric value is to be
displayed, especially in systems consisting solely of digital logic, and not
containing a microprocessor. By utilizing BCD, the manipulation of numerical
data for display can be greatly simplified by treating each digit as a separate
single sub-circuit. This matches much more closely the physical reality of
display hardware—a designer might choose to use a series of separate
identical seven segment displays to build a metering circuit, for example. If the
numeric quantity were stored and manipulated as pure binary, interfacing to
such a display would require complex circuitry.
Therefore, in cases where the calculations are relatively simple working
throughout with BCD can lead to a simpler overall system than converting to
binary.
Background ofBCD Counter

5. BCD to seven segment decoder:
A standard 7-segment LED display generally has 8 input connections, one for each
LED segment and one that acts as a common terminal or connection for all the
internal display segments. Some single displays have also have an additional input
pin to display a decimal point in their lower right or left hand corner.
In electronics there are two important types of 7-segment LED digital display.
1. The Common Cathode Display (CCD) – In the common cathode display, all the
cathode connections of the LED’s are joined together to logic “0” or ground. The
individual segments are illuminated by application of a “HIGH”, logic “1” signal to the
individual Anode terminals.
2. The Common Anode Display (CAD) – In the common anode display, all the anode
connections of the LED’s are joined together to logic “1” and the individual segments
are illuminated by connecting the individual Cathode terminals to a “LOW”, logic “0”
signal.
Proposal Brief

6. NECESSARY MATERIALS
 · R1 - 100K Ohms
 · R2 - 33k Ohms
 · R3 - 330 Ohms
 · R4 - 100 Ohms
 · C1 - 10 uF
 · IC1 - 555 Timer
 · IC2 - 4518 BCD Counter (4520 may be used)
 · IC3 - 4511 BCD to 7 Segment Decoder
 · 4 LEDs
 · 7 Segment Display (Common Cathode, Radio Shack #276-75)
 · +V 9 volts

7. Circuit Diagram

8. HOW THE COUNTER WORKS
555 generates the clock pulse
4518 receives the pulse and starts counting
4511 is a decoder that collect the pulses from 4518 and sends it to the
Display.
Finally the 7 segment LED display shows the output in Decimal
[N.B. when the decimal value reaches 9(binary 1001) in the next step it resets
the clock and goes to decimal o(binary 0000) and start counting again]

9. PIN ASSIGNMENT OF ICS
1. 4518
2. 4511
3. Segment identification of the display

10. 4518 BCD counter timing diagram

11. XILINX MODULE DESCRIPTION
`timescale 1ns / 1ps
module bcd4bit (clk,rst,count);
input clk,rst;
output reg [0:4]count;
always @(posedge clk, negedge rst)
if (rst)
count <= 0;
else
count <= count+1;
endmodule

12. TEST BENCH AND TIMING
DIAGRAM
initial begin
clk = 0;
rst = 0;
end
always #5 clk=~clk;
always #80 rst=~rst;
endmodule

13. Conclusion
Many Important Applications Of BCD :
»»The Atari 8-bit family of computers used BCD to implement floating-point
algorithms. The MOS 6502 processor used has a BCD mode that affects the
addition and subtraction instructions.
»» Early models of the PlayStation 3 store the date and time in BCD. This led
to a worldwide outage of the console on 1st march 2010. The last two digits
of the year stored as BCD were misinterpreted as 16 causing a paradox in the
unit's date, rendering most functionalities inoperable