Binary to BCD code converter

(i) No. of inputs and outputs

Number of inputs = 4

Number of outputs = 5

(ii) Assigning letter symbols

Symbols of inputs – B4, B3, B2, B1

Symbols of outputs – A, B, C, D, E

(iii) Truth table

As the range of BCD is from 0 to 9, a additional bit ‘A’ is taken.  ’A’ is 1 or high when input is more than 9 i.e. it is high for 10, 11, 12, 13, 14 and 15.

INPUT

OUTPUT

B4

B3

B2

B1

A

B

C

D

E

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

1

0

0

1

0

0

0

0

1

0

0

0

1

1

0

0

0

1

1

0

1

0

0

0

0

1

0

0

0

1

0

1

0

0

1

0

1

0

1

1

0

0

0

1

1

0

0

1

1

1

0

0

1

1

1

1

0

0

0

0

1

0

0

0

1

0

0

1

0

1

0

0

1

1

0

1

0

1

0

0

0

0

1

0

1

1

1

0

0

0

1

1

1

0

0

1

0

0

1

0

1

1

0

1

1

0

0

1

1

1

1

1

0

1

0

1

0

0

1

1

1

1

1

0

1

0

1

(iv) Boolean equation

E

All the entries of E­ and B1 are same in truth table.

E = B1

D

Binary to BCD converter ‘D’ truth table

 

D = B4B2 + B4B3B2

C

C = B4B3  + B3B2

B

Through Boolean manipulation we get,

B = B4B3‘B2

 

A

A = B4B3 + B4B2