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 Multipoint Tributary Protocol
Envoy Application Programming Manual—427159-001
5-7
Timeouts
The maximum number of times that Envoy retries an operation encountering an error
indication is specified by the retry count value (RETRIES) when issuing the ADD
DEVICE command. The retry count value can be altered with a call to the SETMODE
procedure. If an error condition persists after the operation has been retried the specified
number of times, an error indication is returned to the application process that requested
the operation.
Timeouts
The protocol uses timeouts to detect error conditions. You designate a timeout value for
each line in one of the following ways:
•
Specify the desired TIMEOUT value when issuing the ADD DEVICE command.
•
Call the SETMODE procedure.
You should always specify a timeout value greater than 2.6 seconds.
Table 5-2
indicates how long Envoy waits during READ and WRITE procedures for
either an acknowledgment or a message from the supervisor station.
An operation that times out is retried the number of times specified by the retry count
before an error indication is returned to the application process. For an application
process acting as a multipoint tributary station, a message received in one call to the
READ procedure is not acknowledged until there is a subsequent call to the READ
procedure. Therefore, the application process at the tributary station must process the
message within the supervisor station’s timeout period. If the message processing time is
longer than the supervisor station’s time, the application process should send a wait-for-
acknowledgment (WACK) sequence at periodic intervals by calling the CONTROL
procedure.
Limited Conversational Mode
The use of limited conversational mode permits a tributary station, following selection
by the supervisor station, to accept a conversational reply in place of a positive
acknowledgment. The application process calls the WRITEREAD procedure to send a
message and to accept a subsequent message from the supervisor station.
Table 5-2. Effect of TIMEOUT Value
During the The TIMEOUT value determines how long Envoy waits for
WRITE procedure An acknowledgment after sending a message to the supervisor
station.
READ procedure after the
tributary station has been
selected
A message from the supervisor station.