数字设计基础 双语教学版 教学课件 作者 英Barry Wilknson 双语课件（第3章）.ppt

3.4 MSI combinational logic devices （2）Applications Address decoder Exp8: Suppose the memory module address to be recognized is 010. D0 D1 D2 D3 D4 D5D6D7 S A2 A1A0 0 Y Multiplexer Y 0 1 0 0 1 0 1 To memory Then output Y is 0, which can be used to activate the memory module. Multiplexer can be used as an address decoder. 3.4 MSI combinational logic devices Logic function generator Apart from its principle function for selecting one data input to feed to a single output, the multiplexer can be used to implement a sum-of-product expression. If a data input is set to a 1 and the data input is selected by the combination of select input values, the Y output will be a 1. Hence by connecting each data input to either a 0 or a 1, depending upon whether the associated minterm is a part of the required function that Y output will implement. 3.4 MSI combinational logic devices Exp9: Implement the function F = ABC + ABC + ABC by using a 8-line-to-1-line multiplexer. D0 D1 D2 D3 D4 D5D6D7 S A2 A1A0 0 Y Multiplexer Y 0 1 ABC F Three data inputs D2, D4 and D7 are set to a 1, the remaining inputs are set to a 0. 3.4 MSI combinational logic devices 3. Arithmetic circuits （1）Addition Half adder The circuit which can add together two binary digits is called a half adder. It has two inputs A, B and two outputs Sum, Carry. Half adder truth table 3.4 MSI combinational logic devices Full adder The circuit which can add two binary digits together with a carry from a previous addition is called a full adder. Full adder has three inputs A, B Cin and two outputs Sum, Cout. Full adder truth table 3.4 MSI combinational logic devices Parallel adder When the carry output of each adder is connected to the carry input of the next higher-order adder, we can get a parallel adder. Let’s take a 4-bit parallel adder as an example: Circuit arrangement of a 4-bit parallel adder 3.4 MSI co