6100 BSC Programming Manual

6100 BSC Link and Station Management
CIRCUIT ASSURANCE State
A station is in CIRCUIT ASSURANCE state if the line is switched,
a connection exists, and ID exchange is required but hasn't been
accomplished. (You express the requirement for ID exchange with
the BSCIDEXCH line parameter.)
TRANSITIONS TO CIRCUIT ASSURANCE STATE. All transitions to
CIRCUIT ASSURANCE state are from DISCONNECTED state. The
following events cause those transitions, provided that the line
is switched and requires ID exchange:
• The application makes a CONTROL request to connect the line.
BSC asserts DTR and waits for DSR. When DSR appears, the
state changes to CIRCUIT ASSURANCE.
• The application makes its first request to read or write from
the line, without first making a CONTROL request. BSC first
makes the connection, as though a CONTROL request had been
issued. The state changes to CIRCUIT ASSURANCE. The same
request may cause another transition: for instance, if
the request performs both connection and ID exchange, the
state goes from DISCONNECTED to CIRCUIT ASSURANCE to CONTROL.
TRANSITIONS FROM CIRCUIT ASSURANCE STATE. The following
events cause transitions from CIRCUIT ASSURANCE to other states:
• The application makes a request that results in ID exchange.
For example, the calling station makes a WRITEREAD request,
sending its ID and reading the reply from the remote station;
the called station makes a READ request to read the ID of the
calling station, then a WRITEREAD request to send its reply.
Once the ID exchange is complete, the state changes to
CONTROL.
• A modem failure causes DSR to drop, or the application
makes a STOP request. The state changes to DISCONNECTED;
BSC reports an error to the application.
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