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
Full-Duplex Protocol
Envoy Application Programming Manual—427159-001
6-3
Full-Duplex/NASDAQ Line Requirements
Communications pass over a full-duplex line like two-way traffic passes over a divided
highway. A full-duplex line enables a station to send messages and receive messages at
the same time. Although full-duplex line facilities are more expensive than half-duplex
facilities, the additional cost usually is offset by the decreased response time and
increased throughput over the line. Full-duplex lines are sometimes referred to simply as
duplex.
Besides being either half-duplex or full-duplex, communications are affected by logical
states that enable either two-way alternate or two-way simultaneous transmission. Two-
way alternate transmission can occur over either half-duplex or full-duplex lines; the
protocol never attempts to transmit simultaneously in both directions. Two-way
simultaneous transmission can occur only over full-duplex lines; the protocol transmits
simultaneously in both directions whenever appropriate. Envoy supports both two-way
alternate and two-way simultaneous transmission.
Full-Duplex/NASDAQ Line Requirements
On Himalaya K-series servers, you used the COUP facility to add two lines on units n
and n+1 of the 3602 controller (where n=0, 2, 4, or 6). To achieve the same effect on
Himalaya S-series servers, you must use MULTI full-duplex or NASDAQ lines (write
and read) on a single line of any CLIP.
On K-series systems, Envoy lines are configured to use communications controllers.
Some of these controllers have units. For example, the 3602 and 6202 controllers have
eight addressable units, numbered 0 through 7. Four of these units are designated as
write (0, 2, 4, 6) and four are designated as read (1, 3, 5, 7).
SWAN concentrators don’t have units, but the UNIT attribute to the ADD DEVICE
command supports the K-series unit numbers.
The following rules apply to the UNIT attribute:
•
You must specify the UNIT attribute when configuring an Envoy DEVICE that is
type (7,30), (7,31), (7,32), or (7,33). If you do not specify the UNIT attribute, the
DEVICE will start but the LINE will not.
•
(7,30) and (7,32) are full-duplex, outgoing (write) lines. (7,31) and (7,33) are full-
duplex, incoming (read) lines.
Figure 6-2. Full-Duplex Lines
009CDT .CDD
Send
Receive