Combinational logic implementation

4/25/00


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Table of Contents

Combinational logic implementation

Implementations of two-level logic

Two-level logic using NAND gates

Two-level logic using NAND gates (cont’d)

Two-level logic using NOR gates

Two-level logic using NOR gates (cont’d)

Two-level logic using NAND and NOR gates

Conversion between forms

Conversion between forms (cont’d)

Conversion between forms (cont’d)

Conversion between forms (cont’d)

Multi-level logic

Conversion of multi-level logic to NAND gates

Conversion of multi-level logic to NORs

Conversion between forms

AND-OR-invert gates

Conversion to AOI forms

Examples of using AOI gates

Examples of using AOI gates (cont’d)

Summary for multi-level logic

Time behavior of combinational networks

Momentary changes in outputs

Oscillatory behavior

Hazards/glitches

Types of hazards

Static hazards

Dynamic hazards

Making connections

Mux and demux

Mux and demux (cont'd)

Multiplexers/selectors

Multiplexers/selectors (cont'd)

Gate level implementation of muxes

Cascading multiplexers

Multiplexers as general-purpose logic

Multiplexers as general-purpose logic (cont’d)

Multiplexers as general-purpose logic (cont’d)

Demultiplexers/decoders

Gate level implementation of demultiplexers

Demultiplexers as general-purpose logic

Demultiplexers as general-purpose logic (cont’d)

Cascading decoders

Programmable logic arrays

Enabling concept

Before programming

After programming

Alternate representation for high fan-in structures

Programmable logic array example

PALs and PLAs

PALs and PLAs: design example

PALs and PLAs: design example (cont’d)

PALs and PLAs: design example (cont’d)

PALs and PLAs: design example (cont’d)

PALs and PLAs: another design example

Read-only memories

ROMs and combinational logic

ROM structure

ROM vs. PLA

Regular logic structures for two-level logic

Regular logic structures for multi-level logic

Combinational logic implementation summary

Author: Gaetano Borriello

Email: cse370-webmaster@cs.washington.edu

Home Page: www.cs.washington.edu/education/courses/370/00sp