Rockwell Automation 8520-9API 9/Series OCI API Developer's Guide User Manual

Page 58

4–10

OCI Data Server Data Items

Publication 8520-6.6 - August 1999

•

Automatic Link. Data that is identified as an automatic link type
is added by the OCI server to the watch list. The value for the
item is then sent from the control to the OCI server and again any
time the data item on the watch list changes. Your application
receives updates to the items each time the value changes on the
control.

OCI

Server

The DDE application requests an automatic data item

from the OCI server. The data server requests the

control add the data item to the 9/Series watch list.

●

9/Series Automatic Link

The 9/Series sends the value to the OCI data server

whenever the item value changes. The OCI server then

passes the new value on to the DDE Application. The

9/Series continues to update the OCI data server every

time the value of the data item changes as long as the

item remains in the 9/Series watchlist.

●

DDE Application

RSLinx

●

The CNC adds the data item to the watch list

and sends the current value of the data item

back to the OCI server.

●

9/Series

CNC

Notify link mode option, though supported by most DDE application
programs, are not recommended. Since the OCI system is designed
to minimize network traffic, notify links are added to the watch list
instead of requiring your server continuously pole the CNC for
status. This nullifies the advantages typically gained by using a
notify link type.

OCI

Server

The DDE application requests an automatic data item

from the OCI server. The data server requests the

control add the data item to the 9/PC watch list.

●

9/PC Automatic Link

The 9/PC sends the value to the OCI data server