Rockwell Automation 8520-9API 9/Series OCI API Developer's Guide - Manual (Page 96)

4–48 OCI Data Server Data Items
Publication 8520-6.6 - August 1999
Format for this data item is % followed by the variable name:
%HDIO1
There can be timing issues related to I/O variables that are altered
through the PAL logic, for example if your OCI station changes a
PAL variable that is later changed in the foreground scan the last
device (PAL logic or the OCI station) that changes the data will be
used.
! User Defined Globals
Data Type
Defined by PAL programmer
Read/Write Read/Write (PAL protected)
Array Index none
Control Type Lathe/Mill/Grinder
You can access all PAL user defined global variables assuming they
have been defined properly in PAL (local PAL variables can not be
accessed). All read and writes are subject to the PAL logic which
always has the authority to override any OCI settings.
Automatic reads of PAL variables are always added to the controls
background watch list. You must consider any timing issues this
may present in your PAL and API applications.
Important: !User Defined Globals do not apply to 9/PC.
Variables set by the OCI occur at the beginning of a PAL scan. The
PAL ladder runs and acts on these changes by writing to the variable
tables. This means if your OCI sets an output to true at the
beginning of a PAL scan, PAL can change the output point back to
false during the PAL scan thus overriding the OCI request to set the
output to true.
Format for this data item is ! followed by the name of the global
variable:
!ARDF
There can be timing issues related to I/O variables that are altered
through the PAL, for example if your OCI station changes a PAL
variable that is later changed in the foreground scan the last device
(PAL logic or the OCI station) that changes the data will be used.