can anyone tell me how to implement a BCD to 8421 code converter?

Question

i thought both are same..but this question was asked for our test.
if anyone knows the difference between them..please explain...

i'm asking for implementation using logic gates..

Answer 1

if BCD = 4 bit Binary Coded Decimal &&
8421 = 4 bit binary then

they are the same.

if you are dealing with more than 4 bits on either side, you have to pad.

for 16 bit BCD , you would add up
binary-nybble[0]*1000 +
binary-nybble[1]*100 +
binary-nybble[2]*10 +
binary-nybble[3]

(nybble is a half byte or 4 bits)

Answer 2

The general assumption is that BCD is formed as 8421 code.
However there are other codes that are used to form BCD, such as 4221, 2421, 5211 etc.

So are you being asked to convert from one of these codes to 8421?
The solution must know the input code to translate. You cannot assume the input code.

Test questions can sometimes contain mistakes.

Answer 3

Dear Bhavya,
For this you would need to specify for how many bits your coder needs to be for example, if it is two digit BCD that means you would require 8 input lines and 4 output lines. because each BCD digit is coded in 4 binary digits. Then there can be packed BCD and Unpacked BCD which is the one you want? Pls clarify.

Regards ,