毕业论文外文翻译--RS232串口通讯（外文原文+中文翻译）Word文件下载.docx

1、 RXD. There are other lines on this port as RTS, CTS, DSR, DTR, and RTS, RI. The 1 and 0 are the data which defines a voltage level of 3V to 25V and -3V to -25V respectively.The electrical characteristics of the serial port as per the EIA （Electronics Industry Association） RS232C Standard specifies

2、a maximum baud rate of 20,000bps, which is slow compared to todays standard speed. For this reason, we have chosen the new RS-232D Standard, which was recently released.The RS-232D has existed in two types. i.e., D-TYPE 25 pin connector and D- TYPE 9 pin connector, which are male connectors on the b

3、ack of the PC. You need a female connector on your communication from Host to Guest computer. The pin outs of both D-9 & D-25 are show below.D-Type-9 pin no.D-Type-25 pin no.Pin outsFunction32RDReceive Data （Serial data input）TDTransmit Data （Serial data output）74RTSRequest to send （acknowledge to m

4、odem that UART is ready to exchange data85CTSClear to send （i.e.; modem is ready to exchange data）6DSRData ready state （UART establishes a link）SGSignal ground1DCDData Carrier detect （This line is active when modem detects a carrier20DTRData Terminal Ready.922RIRing Indicator （Becomes active when mo

5、dem detects ringing signal from PSTNAbout DTE & DCE:Devices, which use serial cables for their communication, are split into two categories. These are DCE （Data Communications Equipment） and DTE （Data Terminal Equipment.） Data Communications Equipments are devices such as your modem, TA adapter, plo

6、tter etc while Data Terminal Equipment is your Computer or Terminal. A typical Data Terminal Device is a computer and a typical Data Communications Device is a Modem. Often people will talk about DTE to DCE or DCE to DCE speeds. DTE to DCE is the speed between your modem and computer, sometimes refe

7、rred to as your terminal speed. This should run at faster speeds than the DCE to DCE speed. DCE to DCE is the link between modems, sometimes called the line speed.Most people today will have 28.8K or 33.6K modems. Therefore, we should expect the DCE to DCE speed to be either 28.8K or 33.6K. Consider

8、ing the high speed of the modem we should expect the DTE to DCE speed to be about 115,200 BPS. （Maximum Speed of the 16550a UART） . The communications program, which we use, has settings for DCE to DTE speeds. However, the speed is 9.6 KBPS, 144 KBPS etc and the modem speed.If we were transferring t

9、hat text file at 28.8K （DCE- DCE）, then when the modem compresses it you are actually transferring 115.2 KBPS between computers and thus have a DCE- DTE speed of 115.2 KBPS. Thus, this is why the DCE- DTE should be much higher than the modems connection speed. Therefore, if our DTE to DCE speed is s

10、everal times faster than our DCE to DCE speed the PC can send data to your modem at 115,200 BPS.What is NULL MODEM?Null modem is used to connect two DTEs together. This is used to transfer files between the computers using protocols like Zmodem protocol, xmodem protocol, etc Figure :Above shows the

11、connections of the Null modem using RS-232D connecterAbove-mentioned figure shows the wiring of the null modem. The main feature indicated here is that the to make the computer to chat with the modem rather than another computer. The guest & host computer connected through the TD, RD, and SG pins. A

12、ny data that is transmitted through TD line from the Host to Guest is received on RD line. The Guest computer must have the same setup as the Host. The signalground （SG） line of the both must be shorted so that grounds are common to each computer.The Data Terminal Ready （DTR） is looped back to Data

13、Set Ready and Carrier Detect on both computers. When the Data Terminal Ready is asserted active, then the Data Set Ready and Carrier Detect immediately become active. At this point, the computer thinks the Virtual Modem to which it is connected is ready and has detected the carrier of the other modem.All left to worry about now is the Request to Send and Clear To Send. As bothcomputers communicate together at the same speed, flow control is not needed thus these two lines are also linked together on each computer. Whe