1. XYZCS 00000 00101 01001 01110 10001 10110 11010 11111 Designing Binary Adders with decoders C(X,Y,Z) =  m(3,5,6,7) S(X,Y,Z) = S m(1,2,4,7);

2. Example: design a full binary adder using one decoder. S(X,Y,Z) =  m(1,2,4,7); C(X,Y,Z) =  m(3,5,6,7)

3. Chapter 2 Encoder Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2009

4. Encoders Perform the inverse operation of a decoder 2 n (or less) input lines and n output lines

5. Encoders

6. Encoders with OR gates

7. Encoders Perform the inverse operation of a decoder 2 n (or less) input lines and n output lines

8. Can be implemented with 3 OR gates A 0 = D 1 + D 3 + D 5 + D 7 ; A 1 = D 2 + D 3 + D 6 + D 7 ; A 2 = D 4 + D 5 + D 6 + D 7 ; If more than 2 inputs are active we need to use priority encoder (priority for inputs) Encoders

9. Accepts multiple values and encodes them Works when more than one input is active Consists of: Inputs (2 n ) Outputs when more than one output is active, sets output to correspond to highest input V (indicates whether any of the inputs are active) Selectors / Enable (active high or active low) Priority Encoder

10. D3D2D1D0A1A2V 0000xX0 0001001 0010011 0011011 0100101 0101101 0110101 0111101 1000111 1001111 1010111 1011111 1100111 1101111 1110111 1111111

11. Priority Encoder