Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols
EnvoyACP/XF Application Programming Manual–132179
3-27
Shutting Down a Data Link
•
To transmit DISC to all the tributaries on the defined station list:
CALL CONTROL 18(fnum)
CONTROL 18 disconnects all responding stations. Nonresponding stations are
placed on the nonresponding list. You must issue READ procedures and check the
returned MCW to determine which stations are not responding.
•
To transmit DISC to a subset of tributaries in the defined station list:
1. Set the poll-bit state to no poll for the tributary stations that should not receive
the DISC.
CALL CHANGELIST(fnum,entry number,1)
2. Transmit DISC.
CALL CONTROL 18(fnum)
•
To transmit DISC to a specific tributary station, turn on bit 0 of the parameter word
and set bits 8 through 15 to the entry number:
CALL CONTROL 18 (fnum,parameter)
parameter
.<0> = 1: Transmits to specified station only
.<8:15> = Station index, referencing station address
in DEFINELIST address list
•
To transmit DISC only to those tributary stations in an error-stop state due to
response timeout failure:
CALL CONTROL 18 (fnum,4)
This use of DISC allows you to perform periodic retries of failed stations.
Self-Disconnecting or Requesting Disconnect
A secondary or tributary station cannot disconnect the primary station. However, the
secondary or tributary station can put itself into Logical Disconnect State or the station
can send a request disconnect (RD) frame to the primary station.
If the secondary station issues CONTROL 18 or CONTROL 18,0, the secondary station
puts itself into the Logical Disconnect State (LDS) and responds with DM to any further
messages (other than a SNRM) from the primary station (Figure 3-6
).
Note. When you use multiple OPEN procedures, you issue a DISC command to only one line
opening. It does not matter which line opening you choose.