6100 MPS-B Programming Manual

6100 MPS-B LINK MANAGEMENT
CONTROL State
CONTROL State
A line is in CONTROL state of a connection exists and the line is
idle (no data transfer activity).
Transitions to CONTROL State
The following events cause transitions to CONTROL state from
other states:
• The application makes a CONTROL request to connect the line.
If the line is leased, the state changes from DISCONNECT to
CONTROL.
• The application makes its first request to read or write from
the line, without first making a CONTROL request. If the line
is leased, the state changes from DISCONNECT to CONTROL.
• The application sends an EOT sequence to end a series of
messages. The state changes from READ or SELECT-TEXT to
CONTROL.
• The retry count is exhausted on either a READ request or
the READ part of a WRITEREAD. The corresponding status codes
are 163, 172, and 177. For status codes 162 and 173, the
completion state is not known. In this case, issue a CONTROL
Send EOT request to ensure a return to CONTROL state. (See
Section 3 for descriptions of the errors.)
Transitions from CONTROL State
The following events cause transitions from CONTROL state to
other states (Figure 2-3 shows various state transitions):
• The application makes a request that results in a successful
I/O operation. For example, it makes a WRITE request to send
the first message; the state changes from CONTROL to
SELECT-TEXT. Alternatively, it makes a READ request to
receive the first message; the state changes from CONTROL to
READ.
• A modem failure causes DSR to drop, or the application
makes a STOP request. The state changes to DISCONNECT;
6100 MPS-B reports an error to the application.
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