6100 MPS-B Programming Manual

6100 MPS-B LINK MANAGEMENT
DISCONNECT State
NOTE
The line states reported in a protocol trace are much more
specific than those described here. For example, the READ
state actually has several substates. This section does not
provide information to help you decode trace data.
DISCONNECT State
A line is in DISCONNECT state if the LIU has been downloaded but
a connection has not been established. Perhaps an earlier
connection was lost, or there is temporarily no caller on a
dialup line. 6100 MPS-B may be waiting for the application to
request a connection, or it may be trying to make a connection--
that is, waiting for DSR to appear after raising DTR.
Transitions to DISCONNECT State
The line begins operation in DISCONNECT state. The following
events cause transitions to DISCONNECT state from other states:
• The application makes a CONTROL request to disconnect the
line. For a switched line, 6100 MPS-B immediately drops DTR;
the line changes to DISCONNECT state when DSR drops. For a
leased line, 6100 MPS-B doesn’t drop DTR; the state changes to
DISCONNECT even if DSR is raised.
• A modem malfunction causes DSR to drop, or the application
process makes a STOP request. The state changes to DISCONNECT
and 6100 MPS-B reports an error to the application process.
Transitions from DISCONNECT State
The following events cause transitions from DISCONNECT state to
other states (Figure 2-2 shows various state transitions):
• The applicaton makes a CONTROL request to connect the line.
For a switched line, 6100 MPS-B asserts DTR and waits for DSR
to raise. When DSR appears, the state changes to CONTROL.
For a leased line, the request does not change DTR or DSR
because both signals are asserted even in the DISCONNECT
state. The request changes the state to CONTROL.
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