Envoy Application Programming Manual

BISYNC Centralized Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
4-29
READ Procedure
Table 4-11 shows the file-system errors that may occur on a continuation READ.
Initial READ (Line in WRITE State)
An initial READ while the line is in the WRITE state (that is, while a tributary station is
selected) causes Envoy, on behalf of the application process, to send an EOT sequence to
the remote station (Example 4-9
). Sending an EOT is the normal method for terminating
a transmission to a tributary station. Following transmission of the EOT sequence, the
action taken is the same as that for an initial READ from the CONTROL state (that is,
polling begins again with the next station in the poll list).
Note. If poll on EOT is enabled, the supervisor polls the next station. The error 163 is not
returned to the application.
Table 4-11. Continuation READ File-System Errors
Error State Description Resultant Line State
0 No error. The message is returned to buffer of
application process.
READ
160 Request is invalid for device state; protocol error. unknown
161 Impossible event occurred for line state. unknown
162 Operation timed out. The acknowledgment was
sent but no message was received within the
timeout or retry limits.
CONTROL
163 EOT received. CONTROL
172 Reply not proper for protocol. The data received
while waiting for a message was not proper for the
BISYNC protocol.
CONTROL
173 Transmission error. The message received was in
error and a NAK sequence was sent the number of
times specified by the retry value.
177 Text overrun. The message received exceeds the
length specified in the read count parameter. The
READ was attempted the number of times
specified by the retry value.
CONTROL
Example 4-9. Initial READ (Line in WRITE State)
Supervisor (Local) Tributary (Remote)
line state = WRITE
CALL READ(...)
| EOT -->
|
v