Data Highway Plus Communication Protocol Overview - Allen-Bradley SLC 500 User Manual

Data Highway Plus
Communication Protocol
Overview
Allen-Bradley PLCs
1
Setting Up the DH+ Network
This appendix provides an overview of the Data Highway Plus (DH + )
communication protocol and explains how the SLC 5/04 processors
support it. This appendix also provides information on the following:
• DH + communication protocol overview
• SLC 5/04 processor and DH + communication
• wiring connectors for DH + communication for SLC 5/04
• typical DH + network configuration
Data Highway Plus implements peer-to-peer communication with a
token-passing scheme to rotate link mastership among a maximum of
64 nodes. Since this method does not require polling, it helps provide
time-efficient reliable data transport. The DH + features:
• remote programming of PLC-2, PLC-3, PLC-5 and SLC 500
processors on your network
• direct connections to PLC-5 processors and industrial
programming terminals
• easy re-configuration and expansion if you want to add more
nodes later
• a communication rate of 57.6K baud, 115.2K baud, or 230.4K
baud
A programming device, such as an IBM-compatible
IMPORTANT
PC, using a 1784-KT Communication Interface
module does not operate faster than 57.6K baud. The
1784-KTX, -KTXD, -PKTX, -PKTXD, and -PCMK can
operate at all three communication rates.
Appendix
Publication 1747-UM011C-EN-P - December 2001
C