Rockwell Automation 8520-9API 9/Series OCI API Developer's Guide - Manual (Page 14)

1–5 Open Control Interface (OCI) Overview
Publication 8520-6.6 - August 1999
Poke requests are only honored by the CNC when they are made
from the data servers controlling OCI station. Refer to the API data
item chapter in this manual for details on requesting control.
!
ATTENTION: Extreme care must be taken when
using the POKE capability. If you inadvertently write
bad data to a critical 9/Series or 9/PC configuration,
you could adversely affect the operation of the CNC.
OCI Data Server Command Requests
Your OCI application can request the CNC to execute a command.
A description of the available CNC OCI commands begins on
page 5–1. Commands ask the control to perform specific tasks such
as download a part program or reformat the RAM disk. When your
application program requests a command be executed for a specific
CNC, the OCI data server passes this command on to the CNC which
will (if valid) execute the command.
OCI Data Server Return and Error Codes
CNCs that are off-line or powered down will not respond to the
requests that the OCI data server is sending them. The OCI data
server will retry a read, write, or command transaction if the
processor is on-line but currently busy. If the OCI data server detects
a severe error, such as no response from the processor, the OCI data
server will stop trying to communicate to the device. After a time
specified in the 9/Series data server’s INI file for the 9/Series CNCs
and in the Configuration Manager for 9/PC CNCs, the OCI data
server will again try to contact the processor. If it fails again, the OCI
data server will repeat the process until the failure no longer exists.
Important: The 9/PC data server is configured via the 9/PC
Configuration Manager.
The retries will affect OCI data server performance, since they entail
additional OCI data server communications.
When your OCI application requests either a data item or issues a
command to the CNC through the OCI data server the request is
either performed or rejected by the CNC.