The document discusses a BCD adder, which is a 4-bit binary adder capable of adding two 4-bit numbers in BCD format and producing a 4-bit BCD output. It explains that the maximum limit for addition in BCD is 9+9=18 before carrying. It also provides the algorithm for BCD addition, which involves adding 6 (0110 in binary) when the sum is greater than 9 and there is a carry, to correctly produce the BCD output. Finally, it mentions that the logic diagram of a BCD adder will be presented.

1. BCD Adder
Presented by
Nokibul Islam Nerob
ID : 191002254

2. Contents
 BCD Adder
 Maximum Limit of Addition
 BCD and Binary Adder Truth Table
 Algorithm for BCD Adder
 Logic Diagram of BCD Adder

3. BCD Adder
 A 4-bit binary adder
 Is capable of adding two 4-bit words having a BCD (binary-coded decimal) format
 Result will be in BCD-format 4-bit output word

4. Limit of Addition
 9 + 9 = 18
 9 + 9 + 1 = 19 (Carry)

5. BCD and Binary Adder Truth Table

6. Algorithm for BCD Adder
 If the sum is up to 9 - regular adder
If the sum is > 9 - must add 6

7. Algorithm for BCD Adder
• Add “0110” when –
i. C* = 1
ii. S3*.(S2* + S1*)
• Finally equation is
C* + S3*.S2* + S3*.S1*

8. Logic Diagram of BCD Adder