Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 11)

Chapter
1
1-1
Data Highway and
Data Highway Plus Overview
In this chapter we provide you with an overview of the Data Highway and Data
Highway Plus cable systems. We describe:
the DH and DH+ cable systems
how nodes communicate on DH
how nodes communicate on DH+
communication between networks
The Allen-Bradley DH and DH+ systems are Local Area Networks (LANs).
They connect programmable controllers, computers, and other devices so they
can communicate and exchange data with one another. A cable system is the
physical means of transmitting this data between nodes. On DH and DH+
networks, a node is a hardware interface.
This manual describes the components of a DH and DH+ cable system and
explains how to construct a network. For the most part, the components and
construction of a DH network are the same as the components and construction
of a DH+ network. There are, however, some differences between the networks.
The types of devices used on the networks, and the communication protocol the
networks use are two of the differences we discuss in this chapter.
This section provides an overview of the Data Highway cable system. In this
section we talk about:
devices used on DH
how nodes communicate on DH
Chapter Overview
The DH and DH+
Cable Systems
DH Overview