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
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Message Formats
However, the Compaq implementation allows the station receiving the
conversational reply to respond with a conversational reply.
Multileaving conversational mode permits each station to maintain contact with the
other by responding with text or with ACK each time text or ACK is received from
the other station. WRITEREAD sends the reply to the station giving the previous
input and obtains the other station's reply.
WRITEREAD is used by the sender to receive a conversational reply and by the
receiver to make a conversational reply. For the sender, a call to WRITEREAD
sends the caller's message; the WRITEREAD completes when the receiving station
returns a message or a positive acknowledgment (if a message is returned, it is
returned in the buffer specified to WRITEREAD). For the receiver, a call to
WRITEREAD is made when the line is in the READ state. This sends the caller's
conversational reply as a positive response to the sender's message. The receiver is
not permitted to call WRITEREAD again until the line is the READ state.
WRITEREAD is used for circuit assurance by the calling (that is, dialing) station.
The calling station sends its identification in the call to WRITEREAD; the called
station's identification is returned in the buffer of the reply message.
Message Formats
A message is defined as the information transmitted over a communications line as a
result of a single call to a READ, WRITE, or WRITEREAD procedure.
The information read from or written to the line buffer area of the application process
consists of two parts: a one-word message control word (MCW) and the message:
where ms is the message size in words (message length in bytes plus one, divided by
two).
The form of the message control word is:
The message control word is not transmitted over the communications line. The message
control word is reflected in the count read or written:
count read or written = 2 + message length
^
(message control word in bytes)
line^buffer[0] = MCW
line^buffer[1:ms - 1] = message
MCW.<0:6> = 0
MCW.<7> = 0 Next incoming message will be acknowledged with ACK0
= 1 Next incoming message will be acknowledged with ACK1
MCW.<8:15> = 0