a means used to ensure the correct order among transmitted safety PDUs and to monitor the communication delay. The MNR starts at a random value and is incremented with each request. It rolls over to a minimum threshold value that is not zero.

Note 1 to entry: Instance of sequence number as described in IEC 617843.

Note 2 to entry: The transmitted MNR is protected by the transmitted CRC signature of the ResponseSPDU.