Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols
EnvoyACP/XF Application Programming Manual–132179
3-26
Shutting Down a Data Link
Sending to Stations in an Error-Stop State
You can issue the mode-setting function only to those stations that have encountered a
response timeout failure (that is, stations in an error-stop state) by using a parameter
value of 4. This feature permits you to perform periodic retries of failed stations.
Shutting Down a Data Link
When stations operate in NRM, only the primary station can shut down the link. The
primary station shuts down the link by issuing a CONTROL 18 call to send a DISC
command.
If the primary station application issues CONTROL 18, CONTROL 18,0, or CONTROL
18,1, the primary station transmits a DISC command. Upon receiving the DISC
command, the secondary station goes into the Logical Disconnect State (LDS). If the
secondary station receives any further frames from the primary station—other than a
SNRM—it responds with a DM (Figure 3-5
).
When the secondary station receives a SNRM, it returns to ITS and transmits a UA,
unless an error condition exists.
In a multipoint supervisor station, the CONTROL 18 operation uses the auto-poll
capability of EnvoyACP/XF. Your application first should issue the CONTROL 18 call,
then issue an AWAITIO call to determine the outcome of the DISC auto-polling.
An application for a multipoint supervisor station can issue a CONTROL 18 call
including any of the following options:
Figure 3-5. Primary Station Issues CONTROL 18
019
Secondary StationPrimary Station
User Issues
CONTROL 18
or
CONTROL
18,0
DISC
Secondary station
goes into
Logical Disconnect
State (LDS).
Any message other than SNRM
DM
UA
SNRM
CONTROL 13