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
3-13
Headings
Headings
Headings use the formats shown in Table 3-7:
Intermediate Text Blocking
The BISYNC protocol allows a message to be divided into segments called intermediate
text blocks (ITB). The use of ITBs allows a single message to be transmitted as a series
of intermediate messages, each of which has its own BCC. Each intermediate block is
checked for errors when it is received, and the entire message is acknowledged when the
last intermediate block (signaled by ETB or ETX) is received.
Intermediate text blocking allows individual (or intermediate) blocks to be checked for
errors and then allows another block to be sent immediately without the need for line
turn-around (that is, the receiver acknowledging each block), as is the case with normal
blocking. If an error is detected during one of the block checks, a NAK is returned only
after an ETB or ETX is received. Then, the entire message containing all of the
intermediate blocks is retransmitted.
Specifying ITB Performance
You can designate Envoy to perform intermediate text blocking by either of the
following ways:
•
Specify an intermediate block length of nonzero value with the ITBSIZE modifier
when issuing the ADD DEVICE command
•
Call the SETMODE 17 procedure.
Envoy provides two methods for intermediate text blocking: one for normal text, the
other for transparent text.
Table 3-7. Formats for Headings
Headings Format Message Length
Heading only SOH-heading-ETB 2 + heading length
Heading and normal
text
SOH-heading-STX-text-ETB
SOH-heading-STX-text-ETX
3 + heading length +
text length
Heading and transpar-
ent text
SOH-heading-DLE STX-text-ETB
SOH-heading-DLE STX-text-ETX
4 + heading length +
text length
Note. The use of ITBs is not supported for the SWIFT protocol.
Note. If you specify an intermediate block length of zero, no intermediate text blocking takes
place.
For normal text, the ITBSIZE includes text and the ITB character.
For transparent text, the ITBSIZE includes just the text.