# Converting 4 4 3 -2 Weighted Code to BCD using Decoder

I've been trying to solve a question - Design a 4 4 3 -2 to BCD converter using decoder.

My attempt at the question was to make the truth table for the 443-2 code and then write the binary equivalents. After that we can group the min terms of each bit of the BCD and therefore through connecting with OR gates we can get the answer.

In Detail - I wrote the truth table for 443-2 code and then wrote the binary equivalent of those bits. In the end some bits were not present as 443-2 is a complementary code which only goes up to 9 and the bits I was getting were

0 , 3 , 5 , 2 , 4 , 11 , 13 , 10 , 12 , 15

The numbers that are not present such as 6,7..... are don't care bits. Now to make a boolean function implementation we find out the min terms and then group them using OR gates ( like making a full adder from a decoder ). For this we will use a 4x16 decoder but what will we do with the don't care bits.

What do we do with the don't care conditions in a decoder?

• couple of things: first: the 0, 3, 5, 2, 4, 11, 13, 10, 12, 15 would be clearer if presented in binary format and listed in a column ....... second: the 6, 7, etc. are not don't care states, they are invalid states ...... your assignment should specify what output should be presented for invalid states .... if the assignment does not specify that, then choose an invalid state output such as 0000 or 1111 and document it in the answer – jsotola Feb 18 at 6:29