Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 670)

OCI Parameters
Chapter 38
38-4
Function
Use this parameter to specify the frequency at which the control checks
data for updated information. The application program running on the OCI
station (for example the AB OCI Basic Display Set) requests data from the
OCI data server as either automatic (updates are automatically sent from
the CNC whenever a data item changes) or manual (updates are only
obtained when the item is initially requested). Both automatic and manual
items are placed on a watchlist at the control which checks this data for
changes and sends updates to the PC when a change occurs (manual items
are deleted from the watchlist after one data transfer). This parameter
specifies the minimum amount of time that can pass before the control will
check the items placed on its watchlist for a value change.
Selecting a longer minimum monitor frequency improves control
performance and keeps 9/Series processor overhead low. Selecting a
shorter minimum monitor frequency allows time critical data changes to be
identified more rapidly to your OCI application.
Axis
Parameter
Number
All [334]
Range
20 to 3000 milliseconds
Notes
This is a global parameter; the value set here applies to all axes.
The actual time between checks may be greater than the minimum time
configured here because of some other higher priority task being executed
by the 9/Series processor. Any time the actual monitor frequency is greater
than the the value configured with this parameter for three scans in a row,
the PAL flag $OCIEN indicates an error. For most applications this error
is not common and can occur at different times during execution without
causing any noticeable performance issues. In the event that many of these
errors are recorded without an equal number of successful scans the control
will display the error message “OCI WatchList Task Overlap” and you
should raise this scan time.
38.3
Monitor Frequency
for Changes