The system structure is shown in the figure below. Suppose two human machine interfaces, HMI 1 and HMI 2, are connected for controlling one programmable logic controller, PLC. HMI 1 represents the first human machine interface which is connected to the PLC via RS-232 communication. HMI 2 represents the second human machine interface which is connected to the DVPEN01 communication module via Ethernet for data exchange between the HMI and PLC. The command areas (control block) of HMI 1 and HMI 2 are assigned by the same data register D of the PLC. When the screens of HMI 1 and HMI 2 are different, and if switching two different screens simultaneously is required, users can use two Screen Open Macros and write the data into data register D of the PLC. No matter if the PLC is controlled by HMI 1 or HMI 2, when one of the Screen Open Macros is executed each time, the different screens of HMI 1 and HMI 2 can be switched simultaneously.
Screen Open Macro of HMI 1
Screen Open Macro of HMI 2
