IS220PDIAH1B  is widely used in various automation systems. Nowadays, it is common to use touch screen plus plc to monitor the equipment, but the touch screen view angle is narrow, not adaptable to harsh environments, and plc data storage capacity is quite limited, not easy to achieve large-scale network interconnection. In view of this, we use the excellent visualisation software visual basic, by the computer plus plc to form a monitoring system. The system not only overcomes the touch screen plus plc monitoring system set up by the shortcomings, but also can complete the real-time monitoring of equipment.

IS220PDIAH1B can use user-defined communication protocol (free port) mode to achieve the communication between computer and plc, plc and plc. Free port communication is the mode of operation in which the s7-200 cpu serial communication port is controlled by the user programme. Using the free port mode enables user-defined communication protocols to connect a variety of intelligent devices. The system parameters have changed, so the monitoring system must have real-time requirements, that is, as soon as the state of the equipment is changed, the monitoring system will collect and transmit the information to the computer, so that the monitoring personnel can understand the scene in time, make a judgement on the scene, and carry out the corresponding operation. Real-time including computer and plc real-time communication and plc real-time monitoring of the state of the equipment associated with two aspects.

IS220PDIAH1B continuously scans the user programme and executes the user tasks. plc in the process of programme execution, based on the considerations of stability, speed, flexibility, etc., the cpu performs the actual input and output operations through the input/output image registers in each scanning cycle, i.e., it reads the value of the actual input point to the image register and writes the value of the image register to the actual output point. As the data reading and writing operations cannot be carried out smoothly in the interrupt, therefore, the characteristics of the plc cyclic scanning execution programme can be programmed to make the data storage area and the input/output image register area exchange data during the scanning period of the programme, that is to say, the computer can achieve the effect of real-time monitoring of the actual input/output points as long as it completes the real-time communication with the data storage area.