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 Point-To-Point Protocol
Envoy Application Programming Manual—427159-001
3-6
Timeouts
SWIFT Retry Values
The SWIFT protocol specifies two fixed retry count values that are required and cannot
be altered by the SETMODE procedure. These retry values are shown in Table 3-3.
Timeouts
The protocol uses timeouts to resolve contention for the line and to detect error
conditions. You designate a timeout value for each line in one of the following ways:
•
Specify the desired value for the TIMEOUT modifier when issuing the ADD
DEVICE command.
•
Call the SETMODE 15 procedure.
Envoy retries an operation that times out. The effect of the timeout value during different
procedures is shown in Table 3-4.
Table 3-3. SWIFT Retry Values
Number of
Retries
Protocol
Sequence Meaning
30 WACK ENQ There can be up to 30 exchanges of the WACK ENQ
sequence, which indicates a temporary not-ready condition
to the sender. This condition should be followed by
receiving text.
30 TTD NAK There can be up to 30 exchanges of the TTD NAK
sequence, which indicates a temporary text-delay negative-
acknowledgment
Note. For the SWIFT protocol, you should not alter the timeout value.
To conform to the BISYNC protocol, the timeout value must be greater than 2.6 seconds. You
should not specify a smaller value. (The default value when issuing the ADD DEVICE
command is 2.7 seconds.)
Table 3-4. Effect of Timeout Value (page 1 of 2)
Procedure Effect of Timeout Value
WRITE Determines the period of time Envoy waits for an acknowledgment after
sending a message to the remote station.
READ Determines the period of time Envoy waits for a message from the remote
station.
Because a message received in one READ operation is not acknowledged until
the next READ operation, the application process must process the message
within the protocol’s timeout period to avoid a timeout at the remote station. If
message processing requires more than the protocol’s timeout period, the
application process should send a WACK sequence at intervals less than the
timeout value by calling the CONTROL procedure.