125720-01 3500/32 External Control Devices

125720-01 3500/32 Failure of external equipment, external equipment is a variety of switches, sensors, actuators, loads, etc. that are directly linked to the actual process. Failure of this part of the equipment, directly affecting the control function of the system can be divided into fixed faults and occasional faults, failure occurs, can be restarted to make the system back to normal, it can be considered occasional faults. Restart can not be restored and need to replace the hardware or software, the system can be restored to normal, it can be considered a fixed fault.

125720-01 3500/32 is widely used as a stable and reliable controller. But it also has some of its own shortcomings, that is, the calculation of data processing and management capabilities are weak, can not provide users with a good interface and so on. The computer can make up for the shortcomings of PLC, it not only has a strong data processing and management capabilities, and can provide users with a very beautiful and easy to operate interface. The combination of PLC and computer can make the system to achieve both timely collection and storage of data, but also can handle and use the data, the key to the combination of the two is the communication between the PLC and the computer.

125720-01 3500/32 to be able to monitor the status of the lower level equipment through the PLC, it is necessary to realize the communication between the host computer and the PLC, general industrial control is to use RS232C to achieve. The host computer first sends a query to the PLC data instructions (actually query the status of the PLC terminals and the value of the DM area, etc.), the PLC receives the instructions on the upper, check (FCS check code) to see if it is correct, if correct, then the upper computer to transmit the data (including the first and last checksum byte). Otherwise, the PLC refuses to transmit data to the upper bit. The upper bit receives the data transmitted by the PLC, but also to determine whether it is correct or not, if it is correct, it receives, otherwise, it refuses to receive.