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1. ELEE 4303 Combinational Circuits Concepts
2. ELEE 4303 Outline Multiplexers
Logic synthesis using multiplexers
Shannon’s expansion
Decoder
Encoder
BCD-to-7-segment display code converter
3. ELEE 4303 2-to-1 multiplexer
4. ELEE 4303 4-to-1 multiplexer
5. ELEE 4303
6. ELEE 4303 Shannon’s expansion theorem Any Boolean function f(w1, …, wn) can be written in the form
Shannon’s expansion can be used multiple times
Multiplexers can be used to implement any Boolean function based on Shannon’s expansion.
7. ELEE 4303 Logic synthesis using multiplexers
8. ELEE 4303
9. ELEE 4303
10. ELEE 4303 Lookup table (LUT) Commonly used logic elements in FPGA
A 3-LUT can realize any logic function of three variables.
A 4-variable function can be realized by three 3-LUTs through Shannon’s expension
11. ELEE 4303 LUT synthesis
12. ELEE 4303 Decoders Inputs: n-bit binary code
Outputs: 2 -bit one-hot code (only one bit is asserted at a time)
Each output corresponds to one valuation of the inputs.
13. ELEE 4303 2-to-4 decoder
14. ELEE 4303 4-to-16 decoder
15. ELEE 4303 Application of decoder--ROM
16. ELEE 4303 Encoders– opposite of decoder
17. ELEE 4303 Priority encoders
18. ELEE 4303 BCD-to-7-segment code
19. ELEE 4303 Comparator
20. ELEE 4303 Exercise Build a 8-to-1 multiplexer using 2-to-1 multiplexers and 4-to-1 multiplexers.
Implement the function
by
1) using a 3-to-8 binary decoder and an OR gate
or 2) using a 2-to-1 multiplexer and any other necessary gates