Envoy Application Programming Manual

ADM-2 Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
7-2
Application Process Interface
Application Process Interface
An application process acting as the supervisor station in an ADM-2 centralized
multipoint network interfaces with Envoy and the various tributary stations by way of
Guardian 90 file-system procedure calls.
Before it can transmit or receive data, the application process must first open a
communications line. Multipoint lines are always opened for exclusive read-write
access. The backup process of the application process can also open the line.
An application process acting as the supervisor must provide Envoy with an address list
containing the poll and select addresses of all the terminals in the network. The
application process passes the address list to Envoy by calling the DEFINELIST
procedure. The format of the address list is described under "Address-List Format" later
on in this section.
This subsection includes:
•
ADM-2 Multipoint Supervisor Polling on page 7-3
•
ADM-2 Multipoint Supervisor Selection on page 7-4
•
Retries on page 7-4
•
Timeouts on page 7-4
Table 7-1. ADM-2 Multipoint Format
ADM-2 Multipoint Format
Individual poll EOT a1 a1 p ENQ
Individual select EOT a1 a1 q ENQ
Sequential select EOT a1 a1 ra2 a2 r...an an s STX-text-ETX LRC
Broadcast select EOT a1 a1 ra2 a2 t...an an s STX-text-ETX LRC
Text block STX-text-ETX LRC
Fast select (for selecting a termi-
nal and transmitting a text block in
one sequence)
EOT a1 a1 s STX-text-ETX LRC
Send function (for passing a one-
character function code to an indi-
vidual terminal)
EOT a1 a1 f ENQ
Notes:
a1, a2, an Specify terminal addresses.
fIndicates function code (tells the terminal what to do).
pIndicates the entry is used for polling.
qIndicates the entry is used for selecting.
sIndicates a one-byte fast select function code.
rIndicates a one-byte sequential select function code.
tIndicates a one-byte broadcast select function code.