DESCRIPTION AND OPERATION
INNIS01 NETWORK INTERFACE SLAVE MODULE
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Exception reports can have data values in the following for-
mats: Digital, analog, and status report. Exception reports are
time-stamped to reflect their processing sequence.
The maximum and minimum report time parameters insure
that an exception report is generated for static or rapidly
changing data. The minimum report time parameter controls
the quantity of exception reports a single rapidly changing
point generates. The maximum report time parameter gener-
ates a periodic report of data items that do not change.
NOTE: If a point goes into or out of alarm, the time parameters are
ignored and the value is reported immediately. Minimum and maxi-
mum exception report times are set through function code 82.
Messages
The NIS module processes four different message types. They
are broadcast, time synchronization, multicast, and NIS poll.
BROADCAST
A node generates a broadcast message when sending informa-
tion to all system nodes. Typically, these messages announce
changes in node status. Broadcast messages include
NODE
ONLINE
,
NODE OFFLINE
,
NODE RESTART
and
NODE BUSY
.
TIME SYNCHRONIZATION
The time synchronization message is a high priority broadcast
type of message. The NIS module services this message type
immediately. Time synchronization provides a common system
time base to be used for sequencing exception reports, access-
ing trend data, and display on a system console.
MULTICAST
A message that contains data for multiple destinations is a
multicast message. This message can have from one to 64
destinations.
NIS POLL
The NIS poll message is a single destination message. The NIS
module uses this message type to request the operational sta-
tus of another node.
MESSAGE FORMAT
Messages exist as frames of information. Each frame consists
of a message control field that follows an information field. The
information field contains the message data. It can consist of
multiple messages and vary in size to a maximum of 1,500
