数字电子的技术pp5.ppt

5-1 Basic Combinational Logic Circuits (Analysis) AND-OR Logic（与-或逻辑电路） AND-OR-Invert Logic（与-或-非逻辑电路） Exclusive-OR Logic（异-或逻辑电路） AND-OR Logic AND-OR Invert Logic Exclusive-OR Logic: XOR gate is actually combination of other gates. 5-2 Implementing Combinational Logic From Boolean expression to logic circuit From truth table to logic circuit From Boolean expression to logic circuit - Given a Boolean expression, create a logic circuit that implements that expression. From truth table to logic circuit - Given a truth table, create a logic circuit that implements that table. 5-3 The Universal Property of NAND and NOR Gates NAND Gate as an Inverter Two NAND Gates as an AND Gate Three NAND Gates as an OR Gate Four NAND Gates as NOR Gate NOR Gate as an Inverter Two NOR Gates as an OR Gate Three NOR Gates as an AND Gate Four NOR Gates as an NAND Gate Assignment: Quiz of EE3314 A commercial airliner has three parallel flight control computers(A,B and C)to provide safe and reliable navigation and flight stability.All three computers perform the same calculations.The airplane must land immediately if more than one computer fails.Each flight control computer is designed to provide a 1(TRUE) when it is operating correctly.The pilot wants a circuit that shows what he should do.The output F should be 1(TRUE) when two or more computers have failed.sketch the circuit using a minimum number of logic gates. a)Construct the truth table b)Minimize the logic function c)Sketch the circuit(using NAND gates) 5-4 COMBINATIONAL LOGIC USING NAND AND NOR GATES NAND LOGIC NOR LOGIC NAND LOGIC A NAND gate can function as either a NAND or a negative-OR gate. Illustration of the use of the appropriate dual symbols in a NAND logic diagram. 5-5 CIRCUIT OPERATION WITH PULSE WAVEFORM INPUTS A B C F Ex 1: 若用与非门实现 Ex 2: implementing by using NAND gates NAND negative-OR NAND logic for X = AB + CD. Development of the AND-OR equivalent. NOR LOGIC A NOR gate