Rockwell Automation 8520-9API 9/Series OCI API Developer's Guide - Manual (Page 12)

1–3 Open Control Interface (OCI) Overview
Publication 8520-6.6 - August 1999
DDE Overview
DDE is a method used by Microsoft Windows to accomplish
process-to-process communications. This common protocol allows a
DDE-compliant Windows application to communicate with another
DDE-compliant Windows application. DDE has been a part of
Windows since version 2.0 and is supported by many of the most
popular Windows application packages, such as MS Excel
t and MS
Word
t for Windows.
The implementation of DDE uses a data server (called the OCI data
server) to send and receive data from the CNC. This data server
provides a DDE interface so other DDE compliant Windows
applications can access data as though the CNC information was
from a local DDE device.
A DDE application must provide three pieces of information to
access a single piece of data from the OCI DDE data server:
•
Service or Application name
•
Topic name
•
Item name
The service for your DDE application will be the Allen–Bradley OCI
DDE data server. The name for this service is:
ABOCISERVER
For the Allen-Bradley OCI data server, a topic is an ethernet alias for
a specific 9/Series CNC. Refer to your OCI Installation Guide for
details on establishing 9/Series ethernet topic names. This alias is
identified in the OCIDSCFG.INI file as the TopicId.
For 9/PC CNCs, the topic name is used to identify a 9/PC (located in
the host computer) to facilitate communication between the 9/PC
CNC executive and various client applications and services running
on a PC. TopicId for the 9/PC CNC is set in the Configuration
Manager.
An item is either a data item or a command item. Data items are
listed starting on page 4–1 and are used to read and write data
from/to your CNC. Command items are listed starting on page 5–1
and are used to request the 9/Series CNC perform a specific task.