The document discusses Binary-Coded Decimal (BCD) adders and their design approaches, focusing on the highest possible numbers that can be represented with 4-bit BCD. It includes specific examples of BCD addition from 0 to 19, detailing how carries are managed and represented in binary. The document also presents various combinations for binary sums with their respective outputs.

1. BCD Adder
UNIT-2
Mohammad Asif Iqbal
Assistant Professor,
Deptt of ECE,
JETGI, Barabanki

2. BCD ADDER

3. BCD Adder. Lest design…
A1 A2 A3 A4 B1 B2 B3 B4
0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
512
COMBINATIONS
IS IT NOT VERY
TEDIOUS???

4. BCD Adder
So before heading towards the new approach, lest again discuss the HIGHEST possible
number in addition of two 4-bit BCD
HIGHEST NUBER USING 4-BIT BCD- 9
HIGHEST NUBER USING 4-BIT BCD- 9
DON’T FORGET TO INCLUDE THE CARRY OF PREVIOUS STAGE-1
19

5. Bcd adder (sum up to 9)
Number C S3 S2 S1 S0
0 0 0 0 0 0
1 0 0 0 0 1
2 0 0 0 1 0
3 0 0 0 1 1
4 0 0 1 0 0
5 0 0 1 0 1
6 0 0 1 1 0
7 0 0 1 1 1
8 0 1 0 0 0
9 0 1 0 0 1

6. Bcd adder (sum is 10 to 19)
Number C S3 S2 S1 S0
10 1 0 0 0 0
11 1 0 0 0 1
12 1 0 0 1 0
13 1 0 0 1 1
14 1 0 1 0 0
15 1 0 1 0 1
16 1 0 1 1 0
17 1 0 1 1 1
18 1 1 0 0 0
19 1 1 0 0 1

7. Bcd adder (sum is 10 to 19)
BCD adder sum Binary sum
Number
C S3 S2 S1 S0
10 1 0 0 0 0
11 1 0 0 0 1
12 1 0 0 1 0
13 1 0 0 1 1
14 1 0 1 0 0
15 1 0 1 0 1
16 1 0 1 1 0
17 1 0 1 1 1
18 1 1 0 0 0
19 1 1 0 0 1
K s3 s2 s1 s0
0 1 0 1 0
0 1 0 1 1
0 1 1 0 0
0 1 1 0 1
0 1 1 1 0
0 1 1 1 1
1 0 0 0 0
1 0 0 0 1
1 0 0 1 0
1 0 0 1 1

8. When is the result>9
Binary sum
Number K S3 S2 S1 S0
10 0 1 0 1 0
11 0 1 0 1 1
12 0 1 1 0 0
13 0 1 1 0 1
14 0 1 1 1 0
15 0 1 1 1 1
16 1 0 0 0 0
17 1 0 0 0 1
18 1 0 0 1 0
19 1 0 0 1 1
C = K +

9. When is the result>9
Binary sum
Number K S3 S2 S1 S0
10 0 1 0 1 0
11 0 1 0 1 1
12 0 1 1 0 0
13 0 1 1 0 1
14 0 1 1 1 0
15 0 1 1 1 1
16 1 0 0 0 0
17 1 0 0 0 1
18 1 0 0 1 0
19 1 0 0 1 1
C = K + S3*S2+

10. When is the result>9
Binary sum
Number
K S3 S2 S1 S0
10 0 1 0 1 0
11 0 1 0 1 1
12 0 1 1 0 0
13 0 1 1 0 1
14 0 1 1 1 0
15 0 1 1 1 1
16 1 0 0 0 0
17 1 0 0 0 1
18 1 0 0 1 0
19 1 0 0 1 1
C = K + S3*S2+
S3*S1

11. 0 0 1 1
0 1 0 1
0 1 0 0 0
0
00
1 0 0 0
0 0 0 0
Inputs:[A]=0101, [B]= 0011, Co=0
1 0 0 0
1

12. THANK YOU!