Electronic – 8 bit octal full adder help

addercomputer-architecturedigital-logic

I have this project listen below and im not sure where to start maybe someone can give me a few pointers or perhaps point me in the right direction of starting this?
Thanks!!

Input: A, B = octal digits (see representation below); Cin = binary digit

Output: S = octal digit (see representation below); Cout = binary digit

Task: Using binary FAs, design a circuit that acts as an octal FA. More specifically,
this circuit would input the two octal digits A, B, convert them into binary numbers, add
them using only binary FAs, convert the binary result back to octal, and output the sum as
an octal digit, and the binary carry out.

Input/Output binary representation of octal digits

Every octal digit will be represented using the following 8-bit binary representation:

Octal 8-bit Input Lines:

Digit: 0 1 2 3 4 5 6 7
0       1 0 0 0 0 0 0 0
1       0 1 0 0 0 0 0 0
2       0 0 1 0 0 0 0 0
3       0 0 0 1 0 0 0 0
4       0 0 0 0 1 0 0 0
5       0 0 0 0 0 1 0 0
6       0 0 0 0 0 0 1 0
7       0 0 0 0 0 0 0 1

You are required to design the circuit in a structured way.

Best Answer

Some hints:

  • Convert the input digit representation to binary (3 bits) for each of both digits using two 3 bit encoders.
  • add both 3 bit digits using a 3 bit adder
  • convert the result back to the required representation using a 4 bit decoder