Through the program determines the touch screen and plc communication failure method

The usual method is to use heartbeat, defined a bool, HMI fixed point set the frequency, PLC receives the point after ON signal is reset. If a period of time, for example, do not receive the points for the ON signal within 5s, it is considered Tongxu interrupted.plc to the memory clock of bytes transmitted to the screen, this screen script-byte value assigned to another address within a plc, plc judge then returned within two bytes of the scan cycle is the same, if the communication is interrupted as described .
 For example, look at Figure, follow these steps:1, the establishment of a data block DB1 in the PLC, which provided two switch “PLC seconds switch” and “man-machine switch response”2, human variable connecting these two variables3, the display unit in the property “PLC seconds switch” variable —- event —- add value change “is negated bit” so that “in response to human-computer switch” variable with “PLC seconds switch” change change .4, PLC programming block, let ‘s PLC switch “reverse every 0.5 seconds, and then let TON delay instruction” man-machine switch response “no action within 1 second output man-machine communication failed because the man-machine communication after abnormal “man-machine switch response” will change no longer occurs.