User Manual

Siemens Building Technologies VISONIK DCS Functions and System Messages VVS18 CM2U8567E / 04.1999
Landis & Staefa Division System Messages --- DCS Messages 3-75
Nr(USDA) Ns(Rx), USDA=yy Rx C=zz
STAP TYP 00:00:00 NAME
Nr(USDA) Ns(Rx), USDA=yy Rx C=zz
->MSGDEV (M.RUSE)
Normal telegrams that are transmitted between the DC Server and each process station
on the ring are provided with two sequence number, Ns
and Nr.
These numbers are the main components of telegram acknowledgement between
"receiver" and "sender". Due to these numbers a distinction can be made between real
repetition in cases of corrupted data and simply duplicated data.
Both frame numbers must always lie within strict limits. If this is not the case, there is an
error somewhere and the numbers or sequence counters must be reset to zero at both
communicating partners.
Because of data integrity, this leads to a re-initialisation of the associated process
station NAME.
The reasons for such a discrepancy between the two frame counters, apart from very
improbable transmission errors, are either in the software of the process station or the
DC Server.
Usually such an error occurs upon initialisation of the communications link because one
of the partners has not cleared its frame counter. The printed information helps localise
the software error.
If a substation detects such an error it requests re-initialisation giving the reason
"?SEQUENCE ERROR" or "SequErr".
If this message occurs on odd occasions, please collect the printouts and send them to
Landis & Staefa FS&PM.
If the error appears regularly with the same PS address, then replace the NAME
controller.
Explanation
Action