Status Snvt - Control Network Solution eNodeIVTM User Manual

either interface has failed the active node will not receive any round trip monitoring packets so
it will report a failure on both interfaces. However it will only report a fault on one. In the same
event the inactive twin will report a failure on only one interface not both. The inactive will
report a fault on one interface.
Alternatively if one interface fails and then some time later the other interface fails, the initially
active twin will not diagnose the second fault. The initially inactive twin, however, will diagnose
the second fault. Therefore in order to fully characterize the failure and fault state of a
redundant pair the state of both devices must be examined. Moreover, the monitoring
application is on the LON side. In the event of an IP failure the alarm SNVT sent by the active
node may not be received by a monitor HMI on the IP side. Although the alarm is sent out both
sides, the IP side has failed so the alarm can't propagate on the IP side and the inactive twin
may not have switched to forwarding mode in time to forward the alarm packet. Nevertheless,
the inactive device will also detect the fault and its alarm will propagate.

3.3.2. Status SNVT

The twin monitoring application has a status SNVT type 93. If bound, the status SNVT is
propagated either on a timer, or when it is updated by the monitoring application, or both, or
neither. If
propagate on update
be scheduled for propagation. In this case the only way to read the status SNVT is to poll it. If
is off and update time is non zero then the status SNVT will propagate at an
propagate on update
interval specified by the update time. If
then the status SNVT will propagate both on the update time interval and anytime the status is
changed. If the update time is zero and
propagate when changed or updated by the monitoring application. Typically the status is
updated when the twin mode state changes.
The fields used in the status SNVT are as follows:
is set to 1 when there is either a monitoring failure or a diagnostic detects a fault.
comm_failure
is not set to 0 until all failures and faults have cleared.
comm_failure
is set based on the system state. See the following table.
reserved2
Bit
7 1 Active State, 0 Inactive State
6 1 Forwarding, 0 Dropping
5 1 Repair State, 0 Not Repair State
4 1 Diagnostic State, 0 Not Diagnostic State
3 1 IP side failure, 0 No IP side failure
2 1 LON side failure, 0 No LON side failure
1 1 IP side fault, 0 No IP side fault
0 1 LON side fault, 0 No LON side fault
September 2011
Copyright © 2011 Adept Systems, Inc. and Control Network Solutions Ltd All Rights Reserved.
is off and the update time is zero then the status SNVT will never
propagate on update
propagate on update
Bit values for reserve2 status byte (big endian)
57
is on and update time is non zero
is on then the status SNVT will only
Value
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