PFSK142 3BSE006505R1通用串行总线串口是计算机上一种非常通用设备通信的协议（不要与通用串行总线UniversalSerialBus或者USB混淆）。大多数计算机包含两个基于RS232的串口。串口同时也是仪器仪表设备通用的通信协议；很多GPIB兼容的设备也带有RS-232口。同时，串口通信协议也可以用于获取远程采集设备的数据。PFSK142 3BSE006505R1串口通讯使用3根线完成：（1）地线，（2）发送，（3）接收。由于串口通信是异步的，端口能够在一根线上发送数据同时在另一根线上接收数据。其他线用于握手，但是不是必须的。串口通信最重要的参数是波特率、数据位、停止位和奇偶校验。对于两个进行通行的端口，这些参数必须匹配：波特率：这是一个衡量通信速度的参数。它表示每秒钟传送的bit的个数。例如300波特表示每秒钟发送300个bit。当我们提到时钟周期时，我们就是指波特率例如如果协议需要4800波特率，那么时钟是4800Hz。这意味着串口通信在数据线上的采样率为4800Hz。通常电话线的波特率为14400，28800和36600。波特率可以远远大于这些值，但是波特率和距离成反比。高波特率常常用于放置的很近的仪器间的通讯。
PFSK142
数据位：这是衡量通信中实际数据位的参数。当计算机发送一个信息包，实际的数据不会是8位的，标准的值是5、7和8位。如何设置取决于你想传送的信息。比如，标准的ASCII码是0～127（7位）。扩展的ASCII码是0～255（8位）。如果数据使用简单的文本（标准ASCII码），那么每个数据包使用7位数据。每个包是指一个字节，包括开始/停止位，数据位和奇偶校验位。由于实际数据位取决于通信协议的选取，术语“包”指任何通信的情况。停止位：PFSK142 3BSE006505R1用于表示单个包的最后一位。典型的值为1，1.5和2位。由于数据是在传输线上定时的，并且每一个设备有其自己的时钟，很可能在通信中两台设备间出现了小小的不同步。因此停止位不仅仅是表示传输的结束，并且提供计算机校正时钟同步的机会。适用于停止位的位数越多，不同时钟同步的容忍程度越大，但是数据传输率同时也越慢。奇偶校验位：在串口通信中一种简单的检错方式。有四种检错方式：偶、奇、高和低。当然没有校验位也是可以的。对于偶和奇校验的情况，串口会设置校验位（数据位后面的一位），用一个值确保传输的数据有偶个或者奇个逻辑高位。
PFSK142
PFSK142 3BSE006505R1 Universal Serial Bus serial port is a very universal protocol for device communication on computers (not to be confused with Universal Serial Bus or USB). Most computers contain two RS232 based serial ports. The serial port is also a universal communication protocol for instruments and meters; Many GPIB compatible devices also come with RS-232 ports. At the same time, serial communication protocols can also be used to obtain data from remote collection devices. PFSK142 3BSE006505R1 serial communication is completed using three wires: (1) ground wire, (2) transmit, and (3) receive. Due to the asynchronous nature of serial communication, ports can send data on one line while receiving data on another line. Other lines are used for shaking hands, but they are not necessary. The most important parameters for serial communication are baud rate, data bits, stop bits, and parity. For two ports that pass through, these parameters must match: Baud rate: this is a parameter that measures communication speed. It represents the number of bits transmitted per second. For example, 300 baud means sending 300 bits per second. When we mention the clock cycle, we mean the baud rate. For example, if the protocol requires a 4800 baud rate, then the clock is 4800Hz. This means that the sampling rate of serial communication on the data line is 4800Hz. The usual baud rates for telephone lines are 1440028800 and 36600. The baud rate can be much greater than these values, but it is inversely proportional to distance. High baud rate is often used for communication between closely placed instruments.
PFSK142
Data bits: This is a parameter that measures the actual data bits in communication. When a computer sends a packet, the actual data will not be 8 bits, and the standard values are 5, 7, and 8 bits. How to set it depends on the information you want to transmit. For example, the standard ASCII code is 0-127 (7 bits). The extended ASCII code is 0-255 (8 bits). If the data uses simple text (standard ASCII code), then each data packet uses 7-bit data. Each packet refers to a byte, including start/stop bits, data bits, and parity bits. Due to the fact that the actual data bits depend on the selection of communication protocols, the term “packet” refers to any communication situation. Stop bit: PFSK142 3BSE006505R1 is used to represent the last bit of a single package. Typical values are 1, 1.5, and 2 digits. Due to the fact that data is timed on the transmission line and each device has its own clock, it is likely that there will be a small unsynchronization between the two devices in communication. Therefore, the stop bit not only indicates the end of the transmission, but also provides an opportunity for the computer to correct clock synchronization. The more bits applicable to the stop bit, the greater the tolerance for different clock synchronization, but the slower the data transmission rate. Parity check bit: A simple error detection method in serial communication. There are four error detection methods: even, odd, high, and low. Of course, without a check digit, it is also possible. In the case of even and odd parity, the serial port will set the parity bit (one bit after the data bit), using a value to ensure that the transmitted data has even or odd logical high bits.
PFSK142
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