6100 ADCCP Programming Manual

Station States and Transitions
ADCCP Link and Station Management
2–10 069225 Tandem Computers Incorporated
Mode-Setting State The mode setting state is the state of a primary or combined station during a mode-
setting sequence. The mode-setting sequence begins from the time that a station puts
a mode-setting frame (DISC, SNRM, SNRME, SARM, SARME, SABM, SABME, SIM, or
RSET) on the line and ends when a UA frame arrives from the remote station. The
state then changes to:
LDS if the mode-setting frame was a DISC
IS if the mode-setting frame was a SIM
ITS for any other mode-setting frame
If the mode-setting sequence times out and retries (L2RETRY) are unsuccessful, the
state changes to the LDS. A secondary station is in MODESETTING state from the
time it receives a mode-setting frame from the primary station until the secondary
sends a UA response to that mode-setting frame.
Initialization State (IS) Initialization State (IS) is the state of a primary or secondary station after a SIM mode-
setting sequence has been completed on the line, but before the primary has issued one
of these frames: SNRM, SNRME, SARM, SARME, SABM, or SABME. The application
controls the initialization state.
Information-Transfer State
(ITS )
Information transfer state (ITS )is the state that a station enters when a primary station
has sent a mode-setting frame (SNRM, SNRME, SARM, SARME, SABM, or SABME),
and the secondary station has responded with a UA. The local station stays in this
state until:
A mode-setting sequence
A modem control request
An error occurs to disconnect the station
The Level 2 Protocol also maintains data on station conditions for use while a station is
in ITS. The application can issue requests to change these conditions. The conditions
on which the Level 2 Protocol maintains data are:
DRNR Occurs when the remote station has transmitted an RNR frame,
indicating that it cannot receive any I-frames. As long as this
condition exists, application requests to send data (SENDTEXT) to the
remote station are delayed.
ERRORSTOP Occurs when ADCCP suspects a line failure or hardware problem in
the remote station. The application receives an asynchronous line
quality report. Application requests to send data to the remote station
fail, and incoming frames from the station (if any arrive) are
discarded. An application CHANGELIST or DEFINELIST request can
clear the ERRORSTOP condition, usually after someone has solved the
line or hardware problem.