基于RS-485的现场总线通信系统克服了RS232通信距离短的缺陷，已广泛应用于工业控制、仪器、仪表、多媒体网络、机电一体化产品等诸多领域。-Based on RS- 485 field bus communication system overcomes the defect of RS232 communication distance is short, has been widely used in industrial control, instruments, meters, mul