《电子技术数字基础 Digital Fundamentals》双语课件-第01章 Digital Concepts.ppt

1 Introductory Digital Concepts Contents Digital and Analog Quantities Binary Digits, Logic Levels and Digital Waveforms Basic Logic Operations (be discussed together with chapter 3) 1-1-1 Digital and Analog Quantities（数字量和模拟量） Electronic circuits can be divided into two broad categories, digital and analog. We are discussing digital electronics(数字电子学） in this term and we will discuss analog electronics （模拟电子学）next term. 1-1-1 Digital and Analog Quantities 1-1-1 Digital and Analog Quantities 1-1-1 Digital and Analog Quantities 1-1-2 Analog Systems 1-1-3 Digital Systems Now most of modern electronic devices and systems are digital system. 1-1-3 Digital Systems 1-1-4 Analog and Digital Systems 1-1-5 ADC and DAC Music in digital form is stored on the compact disk. DAC: digital-to-analog converter Analog signal is got. Another procedure: ADC analog-to-digital converter. 1-2 Binary Digits, Logic Levels, and Digital Waveforms Digital electronics : 2 possible states. 2 states: (1) 2 different voltage levels: HIGH and LOW. (2) switch: open and close. (3) lamp: turned on and off. (4) 2 opposite states. 1-2-1 Binary Digits The two-state number system is called binary(二进制）, and its two digits are 0 and 1. Positive logic (common) (正逻辑）: HIGH=1 and LOW=0. Negative logic (负逻辑） (less common): HIGH=0 and LOW=1 1-2-2 Logic Levels () The voltages used to represent a 1 and a 0 are called logic levels. The figure illustrates the general range of LOWs and HIGHs for a digital circuit. TTL: HIGH 2-5V and LOW 0-0.8V. 1-2-3 Digital Waveforms (数字波形） The pulse: rising (leading) edge (上升沿）and falling (trailing) edge (下降沿）. Pulse width : (脉宽） the duration of the pulse. Period T (周期） : the fixed interval repeated by the periodic pulse . Frequency f: the reciprocal （倒数）of the period. * * An analog quantity (模拟量)is one having continuous (连续的) values. A digital quantity (数字量) is one having a discrete (离散的 )(discontinuous) set of values. High Level（高电平） Low