Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 143)

Publication 1785-UM012D-EN-P - July 2005
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.