Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 46)

Chapter
3
3Ć1
Data Highway Communication
This chapter introduces some of the concepts and terminology involved
with operating the 1775–KA module of the Data Highway.
The Allen Bradley Data Highway is a communication network for
industrial control applications. The Data Highway consists of a central
trunkline cable that may be up to 10,000 feet long. This cable can link
together as many as 64 distinct communication points (or nodes) called
stations.
Each station consists of some type of processor and a station interface
module. The station interface module enables the processor to
communicate with other stations on the Data Highway. The 1775–KA
module is the station interface module for the PLC–3 processor. Table 3.A
lists all possible combinations of station interface modules and processors.
Table 3.A
Station Components
Processor Station Interface Module
PLC-4 Microtrol 1773-KA Communication Interface Module
PLC-3 1775-KA Communication Adapter Module
PLC-2 Family 1771-KA Communication Adapter Module
PLC 1774-KA Communication Adapter Module
Computer or other
programmable
RS-232-C compatible
device
1771-KC/KD/KE/KF Communication Controller
Module
Communication Terminology
Stations communicate with each other by sending messages over the Data
Highway. There are two types of messages:
Command messages
Reply messages
General
Some Terminology