GE DS200SDCCG5AHD驱动器控制卡
端接电阻器的值应等于线路的特性阻抗。对于标准#22 AWG双绞线，这大约为120Ω。应始终使用屏蔽线以尽量减少噪声。极性在RS485通信中很重要：每个设备的每个“+”端子必须连接在一起，系统才能运行。有关串行端口接线的详细信息，请参见第19页第2.2.9节：RS485串行端口。数据格式和数据速率与PQM之间的异步传输的一个数据帧由1个起始位、8个数据位和1个停止位组成，从而形成10位数据帧。这对于高速调制解调器传输很重要，因为Hayes调制解调器不支持比特率大于300bps的11比特数据帧。Modbus协议可以以任何标准通信速度实现。PQM支持1200、2400、4800、9600和19200波特的操作。
The value of the terminating resistors should be equal to the characteristic impedance of the line. This is approximately 120 Ω for standard #22 AWG twisted-pair wire. Shielded wire should always be used to minimize noise. Polarity is important in RS485 communications: each '+' terminal of every device must be connected together for the system to operate. See Section 2.2.9: RS485 Serial Ports on page –19 for details on serial port wiring.Data Format & Data Rate One data frame of an asynchronous transmission to or from a PQM consists of 1 start bit, 8 data bits, and 1 stop bit, resulting in a 10-bit data frame. This is important for high-speed modem transmission, since 11-bit data frames are not supported by Hayes modems at bit rates greater than 300 bps. The Modbus protocol can be implemented at any standard communication speed. The PQM supports operation at 1200, 2400, 4800, 9600, and 19200 baud.
