The usual method of the touch screen manufacturer is to use heartbeat detection to define a bool.
The HMI fixed frequency sets the point, and the PLC resets the point after receiving the ON signal. If the signal that the point is ON is not received within a certain period of time, for example, within 5 seconds, it is considered to be interrupted. The PLC transmits the memory clock byte to the touch screen. The touch screen uses the script to assign the value of this byte to the address in another PLC. Then the plc determines whether the returned byte has the same scan period. If the same indicates the communication interruption. . touch screen
1: PLC and computer should be connected through RS232. Some PLCs have RS232 interfaces, some do not, and no one can be connected to the computer through the adapter.
2: Create a simple project. Put two components, one value display, one value input. The address sets the address in the PLC.
3: The engineering parameter settings must be the same as the settings in the PLC.
4: Click on the online simulation function
This way you can clearly see if the PLC can communicate with the PC. If you can communicate, you can eliminate PLC problems, and parameter settings.