DESCRIPTION AND OPERATION
OPERATION OF SERIAL DATA CHANNELS
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Exception Reporting
The INIIT02 module maintains a database of all points that
send or receive exception reports to or from the remote loop.
The INIIT02 database contains specifications for each point
that helps the INIIT02 module sort and package requests from
other points more efficiently. The interface generates a report
for all destinations every time it receives an exception report
from a point. The INIIT02 module does not monitor the data in
the exception report. Each node is responsible for verifying any
information it receives in an exception report. The INIIT02
module monitors nodes for their status (off-line, on-line, busy).
Control and Configuration Messages
Control and configuration messages do not require a database
within the INIIT02 module. The interface simply passes these
messages through to their destination (unless they are des-
tined for the transfer module). The messages are placed in a
circular buffer through which they pass to the remote loop.
Status Reporting
The INIIT02 module will report its own status. Exception
reporting for status occurs whenever there is a change in sta-
tus or every 60 seconds if no change occurs.
OPERATION OF SERIAL DATA CHANNELS
Command and data transfers between INIIR01 interfaces are
via asynchronous RS-232-C channels. These channels operate
in half or full duplex modes at 75 to 19,200 baud using
eight-bit characters and various combinations of parity and
stop bits.
Messages passed across the serial data channels are formatted
in proprietary message formats optimized for transfer of
INFI-NET data. A sliding window acknowledge protocol is used
wherein each end of the INIIR01 interface can have several mes-
sages outstanding that are acknowledged in sequential order by
the opposite side. Messages are automatically retried until they
are received correctly and acknowledged by the opposite end.
INIIT02 COMMUNICATION PROTOCOL
The INIIT02 communication protocol consists of two layers:
•
Link control layer.
•
Application layer.
The link control layer is a sequenced delivery system with posi-
tive acknowledgment and automatic repeat request for error
