Envoy Application Programming Manual

ADM-2 Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
7-32
WRITEREAD Procedure (Transmit a Send Function)
The file-system errors for a WRITEREAD while the line is in the CONTROL state are
the same as the errors for a continuation READ.
WRITEREAD Procedure (Line in READ State)
A WRITEREAD while the line is in the READ state (that is, a terminal responded to the
poll with text ) is used to acknowledge the preceding message and transmit a send
function to a terminal (Example 7-16
). This procedure usually follows the completion of
a poll sequence in which a function key on a terminal was pressed (that is, a message of
the form SOH f ETX was received). The send function directs the terminal to return
some specified subset of its screen. The data from the terminal is returned in the buffer
specified to WRITEREAD.
The file-system errors for a WRITEREAD while the line is in the READ state are the
same as those for a continuation READ.
Example 7-15. WRITEREAD Procedure (Line in CONTROL State)
Application Process Terminal
line state = CONTROL
MCW.<6> = 1 (message type = special)
CALL WRITEREAD (...)
| EOT a1 a1 sf ENQ -->
| <-- message or EOT
(WRITEREAD completes)
If message received, then line state = READ, error = 0.
If EOT received, then line state = CONTROL, error = 172.
Example 7-16. WRITEREAD Procedure (Line in READ State)
Application Process Terminal
line state = READ
MCW.<6> = 1 (message type = special)
CALL WRITEREAD (...)
| ACK -->
| <-- EOT
| EOT a1 a1 sf ENQ -->
| <-- message or EOT
(WRITEREAD completes)
If message received, then line state = READ, error = 0.
If EOT received, then line state = CONTROL, error = 163.