1. Multiplexers & Decoders By: Jason Pitts CS 147 Spring 2010

2. Information Combinational Circuit (Switch) Multi-input Single or multiple output (mux) Analog or Digital 2 n data inputs, and n address inputs used as a binary number to select one of the data outputs

3. Purpose Simplify Circuits (reduces number of logical gates needed) Cost savings

4. Examples 4 to 1 Channel mux; n = ? __ _ _ Q = abA + abB + abC + abD AddressingInput Selected ba 00A 01B 10C 11D

5. Examples How would you implement an 8 to 1 mux? Hint: 2 3 = 8, therefore n = 3

6. Examples

7. Examples Suppose we want to pick X 5 to be the output. What binary number do the control bits have to be set to in order to achieve this? Answer: 101

8. Examples Since C 0 = 1

9. Examples C 1 = 0

10. Examples C 2 = 1

11. Examples a 2 a 1 a 0 d 7 d 6 d 5 d 4 d 3 d 2 d 1 d 0 | x 0 0 0 - - - - - - - - - - - - - c | c 0 0 1 - - - - - - - - - - - c - - | c 0 1 0 - - - - - - - - - c - - - | c 0 1 1 - - - - - - - - c - - - - - | c 1 0 0 - - - - - - c - - - - - - - | c 1 0 1 - - - - c - - - - - - - - - | c 1 1 0 - - - c - - - - - - - - - - | c 1 1 1 - c - - - - - - - - - - - - | c

12. Examples Can also be made up entirely of AND gates representing a Boolean algebra.

13. Examples AND & OR gates can also be used

14. Decoders: Information Combinational Circuit (Switch) Single or multiple input Multiple Outputs (demux) or Demultiplexers

15. Purpose Full adders Turn a binary input into a different binary output. To be on the other side of a multiplexer to bring the information back to a number of outputs.

16. Examples The full adder

17. Examples Telephony system