Bradley Smoker PLC-5 user manual Monitoring General Status

Communicating with Devices on a DH+ Link 9-11

Monitoring General Status

Status Field	Word(s)	Description
SDA or SDN transmit retry	28	Total number of SDA or SDN messages that were re-transmitted. Some reasons why the station
		would retry a message are:
		the ACK was lost or corrupted on an SDA message, indicating a possible noise problem
		the original message was NACKed
Duplicate node	17	Number of times the station has detected the same station address as itself on the network. As
		a result, the station goes offline.
Claims lost	11	Number of times the station did not win the claim token sequence. See claims won below for
		more information.
Network dead	9	Number of times the station detects no traffic on the network.
		This usually occurs when the station with the token is powered down or is removed from the
		network. The other stations are waiting for the token to be passed to them. Eventually a network
		dead situation is declared and a claim token sequence initiated. (See claims won for more
		information.)
Claims won	10	Number of times the station has won the claim token sequence.
		All the stations initiated a claim token sequence when a network goes down, is just powered up
		and the stations on the network detect that no one has the token, or when a station with the
		token is powered down or removed from the network. A claim token sequence is when all the
		stations on a network attempt to claim the token. When multiple stations attempt to claim the
		token, the lowest numbered station wins.
Dropped token	18	Number of times that the station detected that a duplicate node existed on the link and
		consequently dropped itself off the link

A station determines that there is a duplicate node when it detects that the response to a message or solicit successor is incorrect. For example, if a response is received from a station which was not communicated with, then the sending station assumes that the response is for a packet sent by another station with the same node number. Once the station drops itself off the link, it waits indefinitely to be solicited back into the network. It will only be solicited back into the network if the duplicate node is removed from the link, because station numbers that already exist on the link are not solicited into the network.

Publication 1785-UM012D-EN-P - July 2005