Asynchronous Serial Data Transmission,New words and phrases asynchronous asikrns a.异步的 serial siril a.串行的，串联的 transmission trnzmin n.传输，发送 interface intfeis n.接口 receive risi:v vt.接收，收到 synchronize sikrnaiz vt.（使）同步，（使）同时或同速进行 period pirid n.周期，循环，时期，阶段，时间间隔，时间,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,clock klk n. 时钟 transmitter trnzmit n.发送机，发射机 receiver risi:v n.接收器，接收机 necessary nesisri a.必要的，必须的，必须做的 link lik n.连接，耦合，线路，链路 teleprinter teliprint n.电传打字机 telephone telifoun n.电话 Morse code n.莫尔斯电码,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,signal signl n.信号 native neitiv a.当地的，天生的 fundamental fndmentl a.基本的，根本的，（十分）重要的 split split vt.分开，劈开，分割，分离 incoming inkmi a.进来的，入射的，输入的 stream stri:m n.流，束，潮流，倾向 individual individjul a.分别的，各个的，单独的 unit ju:nit n.单元，元件，成分，装置，设备，组（合），机组，块体,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,group gru: p v.组合，分组，群聚，聚集 character krikt n.字母，字符，符号，字，电码组合，角色，人物 dot dt n.圆点，小数点 dash d n.破折号，长划线，猛冲，冲锋 separate sepreit v.（使）分离，（使）分隔，隔开，区分，分类 intersymbol intsimbl a.码间的，符号间的 intercharacter intkrikt a.字符间的 duration djurein n.持续时间，延续时间,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,examine igzmin v.检查，审查，实验，研究，探讨，测验，考试 divide divaid v.分开，分配，分割，划分，等分 bit bit n.比特 ingenious indi: njs a.精巧的，精致的 format f:mt n.格式，形式 orient : rint vt.定向，定（方）位，标定，（使）适应，朝向 invariably invribli ad.不变的，总是，一定，永恒的,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,comprise kmprais vt.包含，包括，由组成 Plus pls prep.加上，加，外加；a.正的 control kntroul n.控制 frequently fri:kwntli ad.时常，频繁地 correspond krispnd vi.相当，对应，符合，一致 correspond to 相当于，与相对应，与相吻合 与一致 encode inkoud vt.编码 initially inili ad.最初，开头，一开始,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,idle aidl a.闲置的，空闲的 traditionally trdinli ad.传统的，惯例的 mark level 信号电平 logical ldikl a.逻辑的 space level 空号电平 successive sksesiv a.连续的，顺序进行的，逐次的 parity priti n.奇偶性 calculate klkjuleit v.计算,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,continually kntinjuli ad.屡次地，再三地，频频的，连续的 monitor mnit n.；v.监视（器），监测（器） detect ditekt vt.发觉，察觉；n.监测器，侦察器 sample smpl n.样品，取样；vt.抽样，采样 assemble asembl v.集合，收集，装配，组装 flag flg n.旗，标志，标志位 critical kritikl a.决定性的，关键的，危险的，临界的,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,aspect spekt n.方面，方位，外貌，样子 edge ed n.边，边缘，界限，边界，刀刃，刀口 trigger trig v.出发，启动，扣扳机，发射 n.启动，触发，扳机 nominal nminl a.标称的，额定的 thereafter ra:ft ad.此后，其后 situation sitjuein n.位置，地点，场所，形式，情况，环境，局面 obvious abvis a.明显的，明白的，显而易见的,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission,disadvantage disdva:ntid n.不利条件，不利方面，有害，缺点 whenever hwenev ad.无论何时，随时，每当 terminal t:minl n.终端 dump dmp v.倾倒，翻卸，转储 binary bainri a.二进制的,School of telecommunication Engineering, BUPT,Asynchronous Serial Data Transmission1 By far2 the most popular serial interface between a computer and its CRT terminal is the asynchronous serial interface. This interface is so called because3 the transmitted data and the received data are not synchronized over any extended period and therefore no special means of synchronizing the clocks at the transmitter and receiver is necessary4 . In fact, the asynchronous serial data link is a very old form of data transmission system and has its origin in the era of5 teleprinter. Serial data transmission systems have been around6 for a long time and are found in the telephone (human speech), Morse code, semaphore, and even the smoke signals once,School of telecommunication Engineering, BUPT,used by native Americans. The fundamental problem encountered by all serial data transmission systems7 is how to split the incoming data stream into individual units (i. e. , bits) and how to group these units into characters8. For example, in Morse code the dots and dashes of a character are separated by an intersymbol space, while the individual characters are separated by an inter character space, which is three times the duration9 of an intersymbol space. First we examine how the data stream is divided into individual bits and the bits grouped into characters in an asynchronous serial data link. The key to the operation of this type of link is both simple and ingenious. Fig.2-1 gives the format of data transmitted over such a link. An asynchronous serial data link is said to be character,School of telecommunication Engineering, BUPT,oriented10, as information is transmitted in the form of groups of bits called characters. These characters are invariable units comprising 7 or 8 bits of information plus 2 to 4 control bits11 and frequently correspond to ASCII-encoded characters. Initially, whe