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
3-7
Limited Conversational Mode
Limited Conversational Mode
The use of limited conversational mode permits a receiving station to return text in place
of the normal positive acknowledgment. A sender application process on a Compaq
system uses the WRITEREAD procedure to receive a conversational reply. Similarly, a
Compaq receiver application process uses the WRITEREAD procedure to send a
conversational reply.
Multileaving Conversational Mode
The multileaving option is a very limited subset of the multileaving option defined in
IBM document number GA27-3004. The major deviation from the definition is the lack
of a CONTROL state for the data link except when communication is established. No
bidding for ownership of the line takes place once the link is established. After this
initial contact, the link operates in conversational mode, responding to data with data.
The standard definition of BISYNC allows the conversational exchange to occur only
once; the line then returns to the CONTROL state and requires bidding.
Circuit Assurance Mode (ID Exchange)
Following the establishment of a connection on a switched line, an exchange of station
identification (ID) information sometimes takes place. This ID exchange consists of the
calling station transmitting its ID the first time it bids for the line. The ID is checked by
the remote station. If the remote station considers the ID to be valid, it returns its ID
along with a positive acknowledgment. The local station then has the option of checking
the remote station's ID. Following the ID exchange, normal BISYNC transmissions take
place.
The exchange of ID information involves the sending of message sequences that would
be considered improperly formatted messages during a normal transmission sequence.
Therefore, if an ID exchange is to be performed, the line must be configured for ID
exchange when issuing the ADD DEVICE command (IDEXCHG modifier) or ID
exchange must be specified in a call to the SETMODE 16 procedure.
The actual exchange of ID information is performed by calling the WRITEREAD
procedure. A Compaq application process that is the caller sends its ID in a call to
WRITEREAD; a Compaq application process that is the called station returns its ID in a
call to WRITEREAD.
CONTROL
11 or 17
Determines the period of time Envoy waits for the DSR (data set ready) signal
sent by a modem when a transmission begins.
If Envoy does not receive the DSR signal within 8 timeout periods (up to
327.67 seconds), it returns a modem-error indication to the application
process.
Table 3-4. Effect of Timeout Value (page 2 of 2)
Procedure Effect of Timeout Value