Envoy Application Programming Manual

ADM-2 Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
7-29
WRITE Procedure
WRITE of Special Message (Line in CONTROL State)
A WRITE of a special message (Example 7-12) causes Envoy to transmit the message
from the buffer of the application process (the selection sequence is skipped). The call to
the WRITE procedure completes when a terminal acknowledges the message. The
successful transmission of the message is indicated by a condition code of CCE upon
completion of the WRITE.
WRITE of Normal Text Message (Line in READ State)
A WRITE of a normal text message while the line is in the READ state (Example 7-13)
causes Envoy, on behalf of the application process, to acknowledge the preceding
message, read the associated EOT indication, then select the terminal indicated by the
address list entry number in MCW.<8:15> (the entry number is placed in the message
control word by the application process). If the terminal returns a positive
acknowledgment to the selection, the message in the buffer of the application process is
transmitted to it.
Example 7-11. WRITE of Normal Text Message (Line in CONTROL State)
Application Process Terminal
line state = CONTROL
MCW.<6> = 0 (message type = normal)
CALL WRITE(..);
|
| (sel) EOT a1 a1 q ENQ -->
| <-- ACK
| message -->
| <-- ACK
(WRITE completes)
error = 0
line state = CONTROL
Example 7-12. WRITE of Special Message (Line in CONTROL State)
Application Process Terminal
MCW.<6> = 1 (message type = special,
message = sequential select)
CALL WRITE(...)
| EOT a1 a1 ra2 a2 r..an an s STX-text-ETX -->
|
| <-- ACK
(WRITE completes)
error = 0
line state = CONTROL