《电子技术数字基础 Digital Fundamentals》双语课件PPT-第03章 Logic Gates.ppt

3 Logic Gates Contents Basic Logic Operations The Inverter The AND Gate The OR Gate The NAND Gate The NOR Gate The Exclusive-OR Gate The Exclusive-NOR Gate 1-3-1 NOT Logic Operation The NOT operation changes one logic level to the opposite logic level. If the input is HIGH(1), the output is LOW (0), and vice versa. 1-3-1 NOT Logic Operation Function （逻辑功能）: changes one logic level to the opposite level. Changes a 1 to a 0 and a 0 to a 1. 3-1 The Inverter Truth table（真值表）： shows the output for each possible input in terms of levels and corresponding bits. Inverter Truth Table 3-1 The Inverter Inverter operation (反相器运算） For a pulse input, when the input is LOW(0), the output is HIGH(1); when the input is HIGH, the output is LOW, thereby producing an inverted output pulse. 3-1 The Inverter Timing Diagrams （时序图） is basically a graph that accurately displays the relationship of two or more waveforms with respect to each other on a time basis. 3-1 The Inverter ex. A waveform is applied to an inverter in the following figure, show the timing diagram. 3-1 The Inverter –  Logic Expression (逻辑表达式) In Boolean algebra(布尔代数）, which is the mathematics of logic circuits and will be covered in Chapter 4, a variable ( a symbol used to represent a logical quantity) is designated by a letter. The complement of a variable (反变量）is designated by a bar over the letter. A variable can take on a value of either 1 or 0. 3-1 The Inverter – Logic Expression Logic expression（逻辑表达式） for the inverter If the variable is called A and the output variable is called X (中文课本多用F表示),then The complement variable can be read as “A bar” or “not A” （A反）. If A=0, =1 1-3-2 AND Logic Operation（与逻辑操作） 3-2 The AND Gate （与门） The operation is implemented by an AND gate. The basic purpose of an AND gate is to determine when certain conditions are simultaneously true. A possible logic levels for a 2-input(2输入） AND gate 3-2 The AND Gate – Truth Table The tru