Envoy Application Programming Manual

ADM-2 Multipoint Supervisor Protocol
Envoy Application Programming Manual—427159-001
7-28
WRITE Procedure
Table 7-9 lists file-system errors that may occur on a continuation READ.
WRITE Procedure
The WRITE procedure is used to select and transmit a message to a terminal. If the line
is in the READ state when a call to WRITE is made (that is, there is an outstanding
[unacknowledged] message in the network), Envoy acknowledges the message with an
ACK sequence then reads the EOT sequence from the terminal.
WRITE of Normal Text Message (Line in CONTROL State)
A WRITE of a normal text message (Example 7-11) causes Envoy, on behalf of the
application process, to 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. The call to the
WRITE procedure completes when the terminal acknowledges the message. The
successful transmission of the message is indicated by a condition code of CCE upon
completion of the WRITE.
Table 7-9. Continuation READ File-System Errors
Error Numbers Description Resultant Line Number
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 protocol.
CONTROL
177 Text overrun. The length of the
message received exceeds the length
specified in the read count parameter.
Envoy retries the READ (without
sending a NAK) the number of times
specified by the retry value.
CONTROL