PROFIsafe Cycle
Monitoring Number (MNR)
The image shows a safe transmission of PROFIsafe telegrams from the F-Host to the F-Module and back. The transmission is safeguarded with a monitoring number (MNR). The F-Host starts its transmission with the monitoring number MNR_n. After receiving this valid F-PROFIsafe telegram, the F-Module responds immediately with a corresponding telegram with the monitoring number MNR_n. After receiving the response from the F-Module, the F-Host changes the monitoring number to MNR_n1. This mechanism of monitoring number for confirming the transmission between the F-Host and the F-Module also has to be applied for the safe transmission of inputs/outputs and status information (FB inputs) of the F-Module for safe transmission on the part of the IEC application of the F-Module. A signal or FB input (status of the F-Module) has been transmitted safely to the F-Host only if the output signal or FB input has statically applied at least one complete transmission cycle. This means that the FB output S_ValuesToHost_tick_DC has been set two times. With the first impulse of the FB output S_ValuesToHost_tick_DC, the output signal or the FB input is synchronized with the safeguarding mechanism of the transmission. With the second impulse it is confirmed that the transmission to the F-Host has occurred.
