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
ADM-2 Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
7-19
Message Formats
terminal to behave in the same manner as a special message formatted
by Envoy.
MCW.<6> = message type
0 = normal message
1 = special message (fast-select, broadcast-select, and sequential-select)
MCW.<8:15>= entry number. This is a value that indicates an entry in the address list.
A specific entry in the address list, in words, is:
address list[ entry number * address size ]
For polling: Upon completion of a READ where a terminal responded
to the poll with a message, or if an error occurred, Envoy returns the
entry number associated with that terminal.
For normal selection: Prior to calling the WRITE procedure, the
application process must set MCW.<8:15> to the entry number of the
terminal to be selected.
For special-format messages (fast-select, broadcast-selection, and so
on): Whether the message is formatted by Envoy or the application
process, MCW.<8:15> is set to 0.
The message control word is not transmitted over the communications line. The message
control word is reflected in the count read or written (Example 7-8
).
Messages must be formatted prior to transmission. The specific control characters for a
particular message type (normal text, fast-select, broadcast-select, and so on) must be
placed in the message by the application process. If a special-format message is being
sent (such as fast-select), the application process has the choice of letting Envoy insert
the terminal addresses (according to their entry numbers in the address list) into the
message or passing to Envoy a message with the terminal addresses already inserted.
When a message is received, the STX or SOH and ETX control characters are returned
to the application process’s buffer to indicate the type of message received. Note that the
data returned does not contain the longitudinal redundancy check (LRC) character.
Example 7-8. Message Control Word
count read or written = 2 + message length
^
|
(message control word in bytes)