ITEC 352

Lecture 3Low level components(2)

Low-level components

Review

• Electricity• Transistors• Gates• Really simple circuit

Low-level components

Review

• What are

Low-level components

Review #2

• What does this turn into?

Low-level components

Review 3

• What does this do?

Low-level components

Truth tables…

• Draw the truth tables for the following functions:

• F = A’B’C + A’B’C (here the ‘ stands for bar). • F = A’B + B’A

Low-level components

Digital Circuits.

• Consider the following digital circuit.

• Express it as a Boolean algebra expression.

– i.e., F = …? (in terms of A, B, C)– G = …?

Low-level components

MoreFind the boolean expressionCan you optimize it?

Low-level components

Combinational Logic

• Circuits formed using gates.– Key issue: no memory is used in building these

circuits.

Low-level components

Logic Unit

• Translates a set of inputs into a set of outputs • The outputs of a CLU are strictly functions of the inputs, and the outputs are

updated immediately after the inputs change. – NO MEMORY. AS SOON AS INPUT IS GIVEN (after a brief delay due to the

propagational delay) THE OUTPUT SHOWS UP.

Low-level components

Example circuitMultiplexer: Determines which input will reach output

Low-level components

Uses of a MUX

• Routers, Switches Etc… • To implement different other functions. • Multiplexers can be joined together easily.– E.g., Join two 4 X 1 mux’s to get one 8 X 1 mux.

• Example:– Implement the majority function using a Multiplexer

Low-level components

Summary

• Boolean algebra• Truth tables• Mux