10. PLC/terminal communication dialog
PLC
The man/machine communication dialog between the terminal and the
PLC consists of an exchange of data between the two devices.
Various types of data can be exchanged.
Data associated with fields
Command data from the PLC to the terminal
GRAPHIC
TERMINAL
Status data from the terminal
to the PLC
WARNING
UNINTENTIONAL EQUIPMENT OPERATION
If communications between the XBT and PLC are lost, the operator's control over the machine may be lost partially or completely. It is the designer's responsibility to consider programming the PLC logic to account for this situation. One good technique is to monitor Wn+3 of the dialog table from the PLC table.
Failure to follow this instruction can result in death, serious injury,
or equipment damage.
Data associated with the fields
The exchange principle for the data associated with the fields depends on the protocol chosen as a function of the type of PLC. The variables read or written are the single words, double words and word bits.
A - 36 Graphic Magelis
