数电Chapter5.pptVIP

数字电子技术 Code: EI205-001Level: Year 2Lecturer: Zhao, Zhonghua Room: 下院405 Digital Circuits Website: :8090/ Chapter 5 Combinational Logic Chapter Objectives Analyze basic combinational logic circuits Use basic gates to implement SOPPOS expressions Reading Assignment: Chapter 5 (P224~P248) Design a combinational logic circuit for a given Boolean output expression/truth table Write the Boolean output expression for any combinational logic circuit Chapter 5 Combinational Logic 5.1 Basic Combinational Logic Circuits 5.2 Implementing Combinational Logic 5.3 The Universal Property of Extend Gates 5.4 Combinational Logic Using Extend Gates Chapter Outline 5.5 Operation With Pulse Waveforms 5.1 Basic Combinational Logic Circuits Logic Circuit Combinational Circuit Sequential Circuit The output level is at all times dependent on the combination of input level. 5.1 Basic Combinational Logic Circuits 1). AND-OR Logic An AND-OR circuit directly implements an SOP expression, assuming the complements (if any) of the variables are available. A B X C D 1 A B C D X ANSI standard distinctive shape symbols ANSI standard rectangular outline symbols 5.1 Basic Combinational Logic Circuits Truth Table for AND-OR Logic For a 4-input AND-OR logic circuit, the output X is 1 if both input A and input B are 1 or both input C and input D are 1. 5.1 Basic Combinational Logic Circuits 74HC58(CMOS): Dual AND-OR A Specific AND-OR Integrated Circuit 5.1 Basic Combinational Logic Circuits 2). AND-OR Invert Logic When the output of an AND-OR circuit is complemented (inverted), it results in an AND-OR-Invert circuit. POS expressions can be implemented with AND-OR-Invert logic. A B X C D 1 A B C D X 5.1 Basic Combinational Logic Circuits 74LS51 and 74LS54 Specific AND-OR-Inverted Integrated Circuits 5.1 Basic Combinational Logic Circuits 3). Exclusive-OR (XOR) Logic The XOR circuit is considered a type of logic gate with its own unique symbol, it is actually a combination of two AND gates, one