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
Software Concepts
Envoy Application Programming Manual—427159-001
2-6
File-System Error Codes
READ
Accepts incoming data from a remote station. For a multipoint supervisor station,
READ initiates polling of the tributary stations (polling stops when a station
responds with data to the poll; subsequent polling resumes with the next station in
the polling list). For a multipoint tributary station, READ enables the station to
respond to polling or selection.
SETMODE
Alters various line characteristics such as the intermediate block size, the line
statistics threshold, and the number of times that Envoy retries sending or receiving
a message when an error occurs.
WRITE
Transmits data to a remote station. In a point-to-point environment, WRITE is used
to bid for the line. A multipoint supervisor station uses the WRITE procedure to
select and transmit data to a tributary station. A multipoint tributary station, when it
is polled, uses the WRITE procedure to transmit data to the supervisor station. For
an automatic calling unit, WRITE is used to dial a remote station.
WRITEREAD
Performs a WRITE operation followed by a READ operation. The READ operation
is not queued until the WRITE operation completes. Both operations use the same
application buffer.
File-System Error Codes
All of the file-system procedures return a condition code upon completion of the
procedure. The condition code CCE indicates successful completion. A condition code
of CCL or CCG indicates that something out of the ordinary has occurred. If CCL or
CCG is returned, your program should issue a call to the FILEINFO procedure to obtain
an error code that denotes more specifically what has happened. In Sections 3 through
10, the applicable FILEINFO error codes for each protocol are presented in the
description for the particular protocol.
Message Transmission
An Envoy I/O process directly controls the current procedure. Only a single nowait file-
system request may be outstanding at any one time, and it must complete before the next
request can be made. A message is defined as the information transferred over a data
communications line as a result of a single call to a READ, WRITE, or WRITEREAD
procedure:
CALL READ <--- message
In this manual, transmission denotes a logical set of related messages. A transmission is
usually delimited by an EOT control character (as in the BISYNC protocols). A
BISYNC transmission consists of one or more messages (Example 2-1).