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
Asynchronous Line Supervisor Protocol
Envoy Application Programming Manual—427159-001
10-8
File-System Procedures
When a READ operation times out, it returns either of the following things to the
application process:
•
Whatever is left in the buffer
•
A timeout indication
For read-only lines, the application process must issue another READ through file-
system procedures after each block of text is returned. Failure to do so may result in a
buffer overflow and in a loss of data from the read-only line.
File-system timeouts are specified by an AWAITIO call. File-timeouts should be equal
to the sum of the line timeout, plus 100 milliseconds, plus the length of time required to
receive or transmit the block.
File-System Procedures
The application process uses the following file-system procedures to control an
asynchronous line:
AWAITIO
Waits for completion of an outstanding nowait I/O operation.
CLOSE
Terminates access to a data communications line.
CONTROL
Performs the line control operations given in Table 10-4.
DEVICEINFO
Returns the device type and configured record length for a line.
HALTPOLL
Terminates an outstanding nowait READ operation by forcing an immediate return
from the READ with the contents of the read buffer.
Table 10-4. CONTROL Operations for Asynchronous Line Supervisor
Operation Description
11 Waits for data set ready (DSR).
15 Puts a break (space) condition on the line for the configured timeout interval
or until a WRITE is issued (see SETMODE). If the terminal recognizes a
break condition, transmission in the network is suspended.
17 Enables the line by setting the data terminal ready (DTR) signal
18 Disables the line by clearing the DTR signal.