Envoy Application Programming Manual
Table Of Contents
- What’s New in This Manual
- About This Manual
- 1 Application Programming With Envoy
- 7 ADM-2 Multipoint Supervisor Protocol
- 8 TINET Multipoint Supervisor Protocol
- 9 Burroughs Point-To-Point Protocol
- 10 Asynchronous Line Supervisor Protocol
- A ASCII Character Set
- B ASCII to EBCDIC Code Conversion
- C File-System Procedures
- D Statistics Messages
- E S-Series Changes to Envoy
- NonStop™ Himalaya S-Series Server Architecture
- G-Series Migration Considerations
- CBSENSEON and CFSENSEON Modifiers
- LEOTRESYN and NOLEOTRESYN Modifiers
- Treatment of Characters After the Termination Character
- Number of SYN Characters
- DTR Drop
- Reporting of Parity Error
- Half-Duplex Support for Asynchronous Lines
- Controller Replacement
- SYSGEN and COUP
- Unit Numbers
- FDX Line Changes
- No Support for Auto-Call Unit
- Glossary
- Index
BISYNC Centralized Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
4-13
Polling
•
Note that the select list contains multiple entries per station. This permits selection
of individual devices (such as a printer or card punch) at the remote station.
Polling
Polling is initiated by issuing a READ call while the line is in the CONTROL state. The
following terms are associated with polling:
•
Polling Type on page 4-13
•
Polling Interval on page 4-18
•
Poll State on page 4-19
•
Nonresponding Station List on page 4-21
Polling Type
The BISYNC multipoint supervisor protocol supports the following types of polling:
•
Continuous Polling on page 4-13
•
Noncontinuous Polling on page 4-15
•
Specific Polling on page 4-17
Continuous Polling
Continuous polling occurs indefinitely until a tributary station responds to the poll with
text or an error occurs. Continuous polling is specified with the poll type parameter of
the DEFINELIST procedure or the function parameter of the CHANGELIST procedure.
During the polling sequence, Envoy keeps track of the last station polled. The first
station polled when polling resumes is indicated by the next entry in the poll list (the
first station polled when the line is first opened is indicated by the first entry in the poll
list). If a polled station responds with an EOT, the next station in the poll list is polled.
After all stations in the list have been polled once and if another pass is indicated, the
polling sequence continues. Figure 4-3
shows the continuous poll sequence.