串行接口英文翻譯資料

1、<p><b>　　中文2700字</b></p><p>　　RS-232串行接口</p><p>　　RS-232是在任何時(shí)候都常用的接口之一。它不僅已經(jīng)被內(nèi)置于每臺(tái)PC，而且已被內(nèi)置于從微控制器到主機(jī)的多種類型的電腦和與它們連接的設(shè)備。RS-232的最通常得用處是連接到一個(gè)Modem，其他擁有RS-232接口的設(shè)備包括打印機(jī)，數(shù)據(jù)采集模塊，測(cè)試裝置和控

2、制回路。你也可以將RS-232用在任何類型得計(jì)算機(jī)之間的簡(jiǎn)單連接中。</p><p>　　RS-232是設(shè)計(jì)來(lái)處理兩臺(tái)設(shè)備之間的通信的，距離限制為50到100f，這決定于波特率和電纜類型。因?yàn)镽S-232端口被廣泛應(yīng)用，它的另一個(gè)用途是與一個(gè)將這個(gè)接口轉(zhuǎn)換成另一種類型的適配器相連。例如，一個(gè)簡(jiǎn)單的回路將一個(gè)RS-232端口轉(zhuǎn)換成一個(gè)RS-485端口，這個(gè)端口可以和多臺(tái)設(shè)備相連并且可以使用更長(zhǎng)的導(dǎo)線連線。</

3、p><p>　　RS-232連接使用非平衡導(dǎo)線。盡管一個(gè)非平衡的狀態(tài)聽(tīng)起來(lái)像是一些應(yīng)該避免的東西，在這里它僅僅是指導(dǎo)線中的信號(hào)的電氣特性。在一條非平衡導(dǎo)線中，信號(hào)電壓加到一條導(dǎo)線上，所有的信號(hào)電壓都使用一個(gè)公共的接地線。這種類型的接口的另一個(gè)術(shù)語(yǔ)是單端。</p><p><b>　　特性</b></p><p>　　RS---232有幾個(gè)優(yōu)點(diǎn)：&l

4、t;/p><p>　　(1) 它是無(wú)處不在的。每一臺(tái)PC機(jī)都有一個(gè)或更多的RS---232端口。更新的計(jì)算機(jī)現(xiàn)在支持其他諸如USB這樣的串行接口，但是RS---232可以做很多USB無(wú)法做的事情。</p><p>　　(2) 在微控制器中，接口芯片使得將一個(gè)5V串口轉(zhuǎn)換成RS-232變得很容易。</p><p>　　(3) 連接距離可以達(dá)到50到100ft。大多數(shù)的外設(shè)

5、接口都不會(huì)用于太長(zhǎng)的距離。USB連接最長(zhǎng)可以達(dá)到16ft，PC機(jī)的并口打印機(jī)接口與主機(jī)的距離可以達(dá)到10到15ft，或者利用IEEE-1284B型驅(qū)動(dòng)器可以達(dá)到30ft。但是RS-232可以使用更長(zhǎng)的電纜。如果每一個(gè)RS-232端口與一個(gè)Modem相連，你可以使用電話網(wǎng)在世界范圍內(nèi)發(fā)送數(shù)據(jù)。</p><p>　　(4) 對(duì)于一個(gè)雙向連接，你只需要3條導(dǎo)線。一個(gè)并行連接一般需要8條數(shù)據(jù)線，兩條或者更多的控制信號(hào)線，

6、和幾條接地線。所有的導(dǎo)線和更大的連接器使得價(jià)格累計(jì)起來(lái)就比較高了。</p><p>　　RS-232的缺點(diǎn)包括以下這些：</p><p>　　(1) 如果連接的另一頭需要并行數(shù)據(jù)，它不得不將這個(gè)串口數(shù)據(jù)轉(zhuǎn)換成并行數(shù)據(jù)。但是利用一個(gè)UART，這很容易實(shí)現(xiàn)。</p><p>　　(2) 串口是如此的有用，以至于尋找一個(gè)未用的串口可能會(huì)比較困難。PC機(jī)可以有多個(gè)串口，但是

7、一個(gè)系統(tǒng)可能無(wú)法為每一個(gè)串口分配一個(gè)唯一的中斷請(qǐng)求信號(hào)。大多數(shù)的微控制器只有一個(gè)硬件串口。</p><p>　　(3) 在一個(gè)連接中不能有超過(guò)2臺(tái)以上的設(shè)備。</p><p>　　(4) 指定的最大數(shù)據(jù)傳輸速率是每秒20000位。但是，很多接口芯片可以超過(guò)這個(gè)數(shù)值，尤其是在短程連接上。</p><p>　　(5) 很長(zhǎng)的連接需要一個(gè)不同的接口。</p>

8、<p>　　雙向RS-232通信的3個(gè)基本信號(hào)如下：</p><p>　　TD：將數(shù)據(jù)從DCE傳輸?shù)紻CE也被稱作TX和TXD。</p><p>　　RD：將數(shù)據(jù)從DCE傳輸?shù)紻TE。也被稱作RX和RXD。</p><p>　　SG：信號(hào)地。也被稱作GND和SGND。</p><p><b>　　電壓</b>

9、</p><p>　　RS-232的邏輯電平用正負(fù)電壓表示，而不是只用5V TTL和CMOS邏輯的正電壓信號(hào)表示。在一個(gè)RS-232的數(shù)據(jù)輸出（TD），一個(gè)邏輯0被定義為等于或者高于+5V，而一個(gè)邏輯1被定義為等于-5V或者比低于-5V。換言之，信號(hào)使用負(fù)邏輯，在這種邏輯中，負(fù)的電壓為邏輯1。</p><p>　　控制信號(hào)使用相同的電壓，但是使用的是正邏輯。一個(gè)正的電壓表示這項(xiàng)功能為開(kāi)，而

10、一個(gè)負(fù)的電壓表示這個(gè)功能為關(guān)。</p><p>　　RS-232接口芯片反向轉(zhuǎn)換這些信號(hào)。在一個(gè)UART的輸出引腳，一個(gè)邏輯1 數(shù)據(jù)位或者一個(gè)關(guān)控制信號(hào)接近于5V，它在RS-232的接口產(chǎn)生一個(gè)負(fù)電壓。一個(gè)邏輯0數(shù)據(jù)位或者一個(gè)開(kāi)控制信號(hào)接近于0V，它在RS-232接口產(chǎn)生一個(gè)正電壓。</p><p>　　因?yàn)橐粋€(gè)RS-232接收器可能位于一條長(zhǎng)電線纜的末端，等到信號(hào)到達(dá)接收者的時(shí)候，它的電

11、壓可能已經(jīng)削弱了或者加載了噪聲信號(hào)?？紤]到這種情況，在接受方最低要求的電壓要比在驅(qū)動(dòng)器處要低。一個(gè)比+3V高得多的輸入在RD處是一個(gè)邏輯0，或者在一個(gè)控制輸入處是一個(gè)開(kāi)。一個(gè)比-3V要低得多的輸入在RD處為一個(gè)邏輯1，或者在一個(gè)控制輸入處為一個(gè)關(guān)。根據(jù)這個(gè)標(biāo)準(zhǔn)，在-3V和+3V之間的一個(gè)輸入的邏輯電平?jīng)]有定義。</p><p>　　噪聲容限，或者電壓容限，是輸出電壓和輸入電壓的區(qū)別所在。RS-232的大電壓波動(dòng)導(dǎo)

12、致一個(gè)比5V TTL邏輯寬得多的噪聲容限。例如，即便一個(gè)RS-232驅(qū)動(dòng)器的輸出為最小的+5V，它也會(huì)在接受方削弱或者噪聲峰值大到2V，并且仍舊是一個(gè)有效邏輯0。很多RS-232輸出有更寬的電壓波動(dòng)：±9V和 12V是很平常的事情。這些都導(dǎo)致更寬的噪聲容限。最大允許的電壓波動(dòng)是 15V，盡管接受方必須不受任何損害地處理高達(dá) 25V的電壓。</p><p>　　使用的另外兩個(gè)與RS-232有關(guān)的術(shù)語(yǔ)是Ma

13、rk和Space。Space是邏輯0，而Mark是邏輯1。這兩個(gè)術(shù)語(yǔ)是多年以前機(jī)械記錄儀二進(jìn)制數(shù)據(jù)的，他們分別代表物理標(biāo)記和空白。</p><p><b>　　計(jì)時(shí)限制</b></p><p>　　TIA/EIA-232包括最小和最大計(jì)時(shí)規(guī)定。所有的RS-232接口芯片都符合這個(gè)規(guī)定。</p><p>　　指定的旋轉(zhuǎn)速度限制了接口的最大比特率。

14、旋轉(zhuǎn)率是當(dāng)輸出切換時(shí)電壓變化的快慢的量度，并且描述了一個(gè)輸出的電壓變化的瞬間速度。一個(gè)RS-232驅(qū)動(dòng)器的旋轉(zhuǎn)速度必須是每毫秒30V或者更少。</p><p>　　限制旋轉(zhuǎn)速度的好處是它通過(guò)事實(shí)上消除由于電壓偏轉(zhuǎn)引發(fā)的問(wèn)題來(lái)改進(jìn)信號(hào)質(zhì)量，電壓偏移發(fā)生在傳輸有著快速上升和下降節(jié)拍的信號(hào)的長(zhǎng)距離連線上。</p><p>　　但是旋轉(zhuǎn)速度也限制了一個(gè)連接的最大速度。在30V/us的速度下，一個(gè)輸

15、出需要0.3us從+5V切換到-5V。RS-232的規(guī)定的最大波特率為20kbps，這個(gè)速度轉(zhuǎn)換成一個(gè)比特寬度為50us，或者在允許的最快旋轉(zhuǎn)速度下為166倍的切換時(shí)間。</p><p>　　事實(shí)上，因?yàn)閁ART在位的中間附近讀取輸入數(shù)據(jù)，并且還因?yàn)榇蠖鄶?shù)的時(shí)間參考時(shí)鐘是非常準(zhǔn)確的，你可以安全的使用短到5到10倍的切換時(shí)間的位的寬度?？紤]到這些，有的接口芯片允許115kbps或者更高的波特率，即使這違反了這個(gè)標(biāo)準(zhǔn)

16、的建議。</p><p>　　除了有一個(gè)最大的切換速度之外，RS-232 驅(qū)動(dòng)器還必須符合最低標(biāo)準(zhǔn)以確保信號(hào)不在邏輯狀態(tài)之間的未定義區(qū)域停留。對(duì)于控制信號(hào)和其他40bps和更低的信號(hào)，信號(hào)線必須花費(fèi)不超過(guò)1ms的時(shí)間在有效的邏輯1和邏輯0之間的</p><p>　　傳送區(qū)域，對(duì)于其他數(shù)據(jù)和時(shí)間信號(hào)，這個(gè)限制是4%的位寬，或者在20bps下為2us。信號(hào)的上升和下降次數(shù)也要盡可能的接近相等。

17、</p><p>　　在5V邏輯和RS-232之間轉(zhuǎn)換</p><p>　　很多微控制器有異步串口，但是它們的輸出和輸入使用5V邏輯而不是使用RS-232電壓。將5V落連接到一個(gè)RS-232端口需要轉(zhuǎn)換到RS-232電平和從RS-232電平轉(zhuǎn)換到5V邏輯。</p><p>　　利用5V邏輯，我假定了TTL或者CMOS邏輯芯片使用的邏輯電平，這些芯片是由一個(gè)單一的+5

18、V電源供電，信號(hào)電平以接地電平作為參考。</p><p>　　對(duì)于TTL邏輯，一個(gè)邏輯低輸入不高于0.8V。一個(gè)邏輯高輸出必須至少為2.4V，而一個(gè)邏輯高輸入必須至少為2V。利用這些邏輯電平，一個(gè)接口可以有0.4V的噪聲信號(hào)而不至于產(chǎn)生錯(cuò)誤。</p><p>　　這些邏輯電平應(yīng)用在初期的，標(biāo)準(zhǔn)的7400系列的TTL邏輯和他的派生系列，包括74LS74F和74ALS TTL。較早的利用NMO

19、S技術(shù)制造的微控制器也使用這些邏輯電平。</p><p>　　大多數(shù)的CMOS芯片定義了不同的邏輯電平，并且有更寬的噪聲容限。一個(gè)邏輯低CMOS輸出不高于0.1V，而一個(gè)邏輯低輸入可以高達(dá)20%的電源電壓，或者對(duì)于5V的電源輸入可以達(dá)到1V。一個(gè)邏輯高輸出至少為4.9V，而一個(gè)邏輯高輸入必須至少達(dá)到電源電壓的70%，或者對(duì)于5V電源輸入而言達(dá)到3.5V。使用這樣的邏輯電平的系列包括4000系列，74HC和74AC

20、。</p><p>　　有的CMOS芯片有TTL兼容輸出。這是得他們可以直接和CMOS或者TTL邏輯項(xiàng)鏈。遵循這個(gè)慣例的芯片包括74HCT邏輯系列和大多數(shù)的微控制器。</p><p>　　RS-232 Interface</p><p>　　RS-232 is one of the normally used interfaces at any time, it n

21、ot only built in every PC-set, but also built in any types of computers which are from microcontroller to host computers, and equipment connected with them. The general usage of RS-232 is to connect a modern, the other a

22、rrangements with RS-232 interfaces include printer, data collection module, testing device and control loop. RS-232 can be also used in the simple link of any type of computer.</p><p>　　RS-232 is designed to

23、 deal with the communication between two arrangements with distance limitation from 50 to 100ft, which depend on Potter rate and type of electric cable. Because of wide application of RS-232 port, its other usage is to l

24、ink another type of adapter converted form the port.</p><p>　　For example, a simple loop changes a RS-232 into a RS-485 port. The port can be link with several devices by means of a long lead. Non-equilibriu

25、m lead is used to linked to RS-232. Although non-equilibrium should something avoidable, it only refers to the electric property of the signal in lead. In a non-equilibrium lead, signal voltage is applied to another lead

26、, all has another technical term “signal end”.</p><p>　　Advantages in RS-232</p><p>　　RS-232 is used everywhere. Every PC-set has one or more RS-232 ports. The renewed computers sustain other se

27、rial interfaces like USB. But RS-232 can do many things which USB can’t do.</p><p>　　In the micro-controller interface chip can be easily used to change into RS-232.</p><p>　　The jointing distan

28、ce can reach 50-100ft. Many external interfaces are not used for too long distance. The longest distance joint of USB can reach 16ft. The distance between parallel printer interface on the PC-set and the host computer ca

29、n reach 10 to 15ft, or 30ft by using Type TEEE-1284B driver. But RS-232 can use the longer electric cable.</p><p>　　If every RS-232 port is linked with a modern, Telephone network can used to send data in th

30、e rage of the world.</p><p>　　For a double link, 3 leads are needed. A parallel circuit generally needs 8 data lines, two or more control signal lines and ground wires。It is more expensive if more leads and

31、bigger connectors are used.</p><p>　　Disadvantages in RS-232</p><p>　　If one side of link needs parallel data, it has to transform serial into parallel data. But if it is easily realized a UART

32、is used.</p><p>　　Because of the serial port so useful, it is maybe harder to look for a free serial port PC-set may have many serial ports, but a system maybe can’t distribute a sole breaking enquiring sign

33、al to every serial port. Most micro-controller only has one hardware serial port.</p><p>　　No more than 2 set in one link.</p><p>　　The biggest designated transmitting rate of data is 2000bits/s

34、.But many interface chip can surpass this numerical value, especially in the short distance link.</p><p>　　A longer link needs a different interface.</p><p>　　3 basic signals of the double RS-23

35、2 communication as follows:</p><p>　　TD. Transform data DTE to DCE It’s also called TX and TXD.</p><p>　　RD. Transform data DCE to DTE It’s also called RX and RXD.</p><p>　　SG. Sign

36、al land. It’s also called GND and SGND.</p><p><b>　　Voltage</b></p><p>　　Logic0 is a positive RS-232 voltage, the logic electric level of RS-232 is indicated with positive-negative,

37、and not only use the positive voltage signal of the 5VTTL and CMOS logic to indicate. In the data logger(TD)of RS-232，a logic0 is defined equal to or higher than +5V, and a Logic1 defined equal to -5V or lower than -5V.

38、In another word, signal use the negative logic, in this logic, the negative voltage is Logic1.</p><p>　　Control signal uses the same voltage, but it uses positive logic. A positive voltage indicates this fun

39、ction is on and a negative voltage indicates this function is off.</p><p>　　RS-232 interface chip transform these signals in reverse. In output pin of one UART, A logic1 datum or a off control signal is clos

40、e to 5V, it produces negative voltage on the interface of RS-232.A logic0 datum or an on-control signal is close to 0V, it produces a positive voltage on the interface of RS-232.Because of the RS-232 receptor maybe at th

41、e end of a long electrical cable, when the signal reaches the receiver, it’s voltage is probably weaker or with the noise signal. In consideration of</p><p>　　An input higher than +3V on the RD are a Logic0,

42、 or on a control input is open. An input lower than -3V on the RD are a Logic1, or on a control input is off. According to this standard, input logic electrical level between -3V and +3V have no definition</p><

43、;p>　　Noise tolerable limitation or voltage tolerable limitation is difference output voltage and input voltage. The big voltage undulation from RS-232 lead to a noise tolerable limitation wider than logic5TTL. For exa

44、mple, even thought a output from RS-232 driver is the smallest +5V,it’s also be weaken in the receiver or the noise peak rise to 2V, and still is a effective Logic0.Many outputs from RS-232 have the wider voltage undulat

45、ion : ±9V and ±12V are very common affairs. All these affairs can le</p><p>　　The other two technical terms concern with RS-232 to be used is Mark and Space. Space is Logic0 and Mark is Logic1. The

46、se two technical terms which was used by the machine recording instrument to record binary data in many years ago, each of them are representation physical and blank.</p><p>　　Clocking Limitation:</p>

47、<p>　　TIA/EIA-232 including smallest and biggest clocking stipulate. All out the RS-232 interface chips all accord this stipulate.</p><p>　　Appointed revolving speed limited the biggest Potter rate of

48、interface.</p><p>　　The revolving rate is measure to the rate of speed change when output cut-over voltage, and describe the change of instantaneous velocity in The advantage in limited the revolving is for

49、improve signal quality by in the matter of fact to limited the problem which is due to voltage deflection, voltage deflection occur the signal in the long distance link which has high-speed rise and descend. There more d

50、etailed narrations to this problem are in capter10.</p><p>　　But revolving velocity also limited to the biggest speed of a link. Under speed of 30V/μs, a output need 0.3 μs to cut-over time in 166 times.<

51、/p><p>　　Actually, because the UART to read input data in near the middle of the digit, and also because many time’s consult clock in very accurate, usually can may use the digit width for cut-over time as shor

52、t 5 to 10 time safety. Considered these conditions, some interface chips permitting 115kbps or more higher Potter rate, even though its infringe the suggestion this standard.</p><p>　　Except for has a bigges

53、t cut-over velocity, RS-232 driver also must according the lowest standard to ensure the signal no stopover in the undefined area between the logical condition. To control signal other 40bps and the lower signal. Signal

54、lines must spend time not surpass 1μs in the transmit area between the effective Logic1 and Logic0.To other data and time signal this limitation place wide is 4% or under 20 bps is 2μs. Frequencies of signal rise and des

55、cend also probably close to be equal.</p><p>　　Transformation between 5V logical and RS-232</p><p>　　Many micro-controllers have asynchronous serial ports, but their input and output rather to u

56、se 5V logic than to RS-232 voltage. To link 5V logic to a RS-232 port need to transform into RS-232 electrical level and transform from RS-232 electrical level into 5V logic</p><p>　　To use of 5V logic, I su

57、pposed to the use of electrical level of TTL or CMOS logic chips, these chips are supply electricity by a single +5V electrical, signal electrical level refer to grounding electrical level. Tables 6-2 indicate this. I al

58、so supposed to positive logic, in here, the logical high electric level is logic1.</p><p>　　To TTL logic, a logical low output must below 0.4V, a logical low input must below 0.8V. A logical high output must

59、 be 2.4V at least and a logical high input must be 2V at least. To use of these logical electrical levels, an interface may have noise signal at 0.4V and not necessarily to make mistake.</p><p>　　These logic

60、al electrical levels are used into TTL logic of early days standard 7400 series and other drivers series, including 74LS 74F and 74AL STTL. The NMOS technology early is used to make micro---controllers also use these hel

61、ical electrical levels.</p><p>　　Most CMOS chips definite different logical electrical levels and have wider noise tolerable. A logical low CMOS output below 0.1V and logical low input may higher to 20% elec

62、trical voltage, or to electrical voltage in 5V can reach to 1V. A logical high output to be 4.9V at least and logical high input must reach to electronically voltage’s 70% at least, or to 5V electrical input reach to 3.5

63、V. To use of this series of logical electrical level, including 4000 series, 74HC and 74AC logic. </p><p>　　Some of CMOS chips have TTL compatible input and CMOS compatible output. Its make them can link