【正文】 1 中文 4700 字 The Designing of Serial Communication Based on RS232 Abstract This paper discussed the principle of serial munication mainly, proposed the design method based on RS232, designed the hard circuit of serial munication, and realized the programming to PC Microputer and single chip microputer by using assembly language and C++ Builder separately. Keywords: serial munication。 single chip microputer。 program design. I. INTRODUCTION During working in the control system, the PC microputer sends instructions for stepbystep motor to collect the image information. Therefore the munication between the PC microputer and the driving system is needed for the munication system. In general, a plete munication system consists of transmitter, receiver, converting the data interface and transmitting data channel. The control of the stepbystep motor is realized through the pulse distribution by single chip microputer. On the motor control system, the PC microputer is called as upper puter, and the single chip microputer for driving stepbystep motor is called as lower puter. The munication between the upper puter and the lower puter has two methods, that is to say the parallel munication and serial munication. Parallel interface can transmit much data at the same time and has the fast speed, but when the transmission distance is far and the number of data is much, it needs more the number of transmission lines. In addition, the voltage level may be changed by the transmission line factor and electromagic interference. Serial munication is a one way that the data is transmitted by a bit in order, in which two transition lines is needed to realize bidirectional munication. It is taken into consideration that the data is much and the transmutation number is little, the serial munication is utilized in the control system so as to simplify the hardware and save the cost. Serial munication is one of the oldest mechanisms for devices to municate with each other. Starting with the IBM PC and patible puters, almost all puters are equipped with one or more serial ports and one parallel port. As the name implies, a serial 2 port sends and receives data serially, one bit at a time. In contrast, a parallel port sends and receives data eight bits at a time, using eight separate wires. For serial munication to work, you just need a minimum of three wires—one to send, one to receive, and one signal ground. For parallel munication, you need eight wires. Despite the paratively slower transfer speed of serial ports over parallel ports, serial munication remains a popular connectivity option for devices because of its simplicity and costeffectiveness. It shows some of the devices that use a serial port to connect to the puter. Using a serial port, you can connect to a modem, a mouse, or a device such as a bridge/router for configuration purposes. II. THE BRIEF DESCRIPTION OF SERIAL PORT COMMUNITION Serial munication is the munication between sender and receiver data transfer is in the single data line, to move each time a bit. The advantage is that only a pair of transmission lines to send information, so its low cost, suitable for longdistance munications。 its disadvantage is that transmission speed is low. As mentioned, a serial device sends and receives data one bit at a time. Some devices can send and receive data at the same time and are known as fullduplex devices. Others that can either send or receive at any one time are known as singleduplex. To initiate transmission, a device first transmits a start bit, followed by the data bits. The data bits can be five, six, seven, or eight bits, depending on what has been agreed upon. Both the sender and the receiver must be set to the same data bits for munication to take place correctly. Once the data bits are sent, a stop bit is sent. A stop bit can be one, one and a half, and two bits. The baud rate is the speed of transmission of data from one device to another. Baud rate is usually measured in bits per second (bps).Most serial devices transmit in seven or eight bits. To detect that the data has been sent correctly, an optional parity bit can be included together with the data bits. A parity bit can be one of the following: odd, even, mark, space, or none (mark and space parity are almost always used). Using a parity bit provides a basic mechanism to detect corruption of data that was sent and does not guarantee that the data received is free from error. Nevertheless, a parity bit is useful for improving the integrity of the data sent. Most serial ports adhere to the RS232C standard, which specifies a connector either with 25 pins or with 9 pins. Most serial devices use the ninepin connector. Serial munication with asynchronous munication and synchronous munication are two basic means of munication. Synchronous munication for the case of high transmission speed, the hardware plexity. The asynchronous munication 3 used in transmission speed between 50 and 19200 baud. Transmission is r