6100 MPS-B Programming Manual

SECTION 2
6100 MPS-B LINK MANAGEMENT
This section describes two important aspects of 6100 MPS-B
operation:
• The five major states through which a communication link
moves, and the events that cause transitions between states.
Some application requests have different meanings in different
states, and error messages can indicate unexpected state
transitions.
• The modem signals 6100 MPS-B uses, and the events that cause
them to change. You need information about this interface to
choose and strap a modem, to select line parameters consistent
with your equipment and application, and to diagnose line and
modem errors.
You should at least look at the information in this section
before reading Section 3. Later, you might find the lists and
diagrams helpful as summaries.
LINE STATES AND TRANSITIONS
6100 MPS-B is realized as a "state machine." At a given time, a
line is in one of five major states. Application requests and
arriving data are events that can cause state transitions. Only
certain events are allowed in each state; for example, you cannot
send data if the line is disconnected, and you cannot change line
parameters unless the line is disconnected.
A simplified view of 6100 MPS-B states and transitions is shown
in Figure 2-1. The states and transitions are described, in
detail, on the pages that follow the figure.
2-1