PDOs

SendCounter

TxPDOs feature an additional SendCounter variable under the Control menu item.

By default, PDOs are sent automatically when a change is made. This variable can be used if the data is to be sent not only when a change is made, but also when nothing has changed in the data in the PDO.

The variable must therefore be incremented by one if the data in the PDO is to be sent even without a change. If the variable is incremented in the same cycle and a change of data is made in parallel, only one telegram is sent.

Apart from this scenario, this variable can be used to monitor whether the corresponding PDO was sent when the data changed.

ReceiveCounter

RxPDOs feature an additional ReceiveCounter variable under the Status menu item.

The input variable is incremented by one whenever a PDO is received. In this way newly arrived PDO are always logged, even if the data in the PDO are unchanged. The variable also indicates whether a device is still sending data on a regular basis. It is useful to link variable with the PLC and monitor it.