Envoy Application Programming Manual

Envoy Application Programming Manual—427159-001
5-1
5
BISYNC Multipoint Tributary Protocol
A BISYNC centralized multipoint network Envoy consists of two or more stations
communicating over a leased multidrop line with one station designated as the
supervisor and the other stations designated as tributaries.
This section describes the binary synchronous communication protocol used by an
application process acting as a tributary station in a BISYNC centralized multipoint
network. The tributary responds to poll and select sequences issued by the supervisor.
Topics discussed in this section include:
•
Protocol Capabilities on page 5-1
•
Application Process Interface on page 5-2
•
File-System Procedures on page 5-8
•
Address-List Format on page 5-11
•
Poll and Select States on page 5-14
•
Message Formats on page 5-15
•
File-System Errors on page 5-19
•
Line Action by Procedure Call on page 5-20
•
Line-Error Handling on page 5-29
•
Programming Examples on page 5-35
Protocol Capabilities
The Envoy BISYNC multipoint tributary protocol conforms to the Binary Synchronous
Communications (BISYNC) standard described in the IBM document no. GA27-3004-2
for centralized multipoint communication. The protocol includes the following
capabilities:
•
ASCII or EBCDIC line code
•
Check-character generation and verification performed by Envoy hardware (retries
of operations in error are performed automatically by Envoy)
•
Data-link control through the use of established data-link control character
sequences
•
Timeouts designated on all line operations according to established BISYNC
standards
•
Limited conversational mode
•
Support for the message formats shown in Table 5-1.