Rockwell Automation 1747-L5xx SLC 500 Modular Hardware Style User Manual - Manual (Page 181)

181 Publication 1747-UM011G-EN-P - June 2008
Appendix
B
Setting Up the DH-485 Network
The information in this appendix will help you plan, install, and
operate the SLC 500 processor in a DH-485 network. This chapter also
contains information that describes the DH-485 network functions,
network architecture, and performance characteristics. It also covers:
• DH-485 network description.
• DH-485 network protocol.
• DH-485 token rotation.
• DH-485 network initialization.
• devices that use the DH-485 network.
• 1747-AIC isolated link coupler for DH-485.
• 1747-UIC USB to DH-485 interface converter.
• example system configuration
(includes 1761-NET-AIC advanced interface converter).
• important planning considerations.
• installing the DH-485 network.
DH-485 Network
Description The DH-485 network passes information between devices on the
plant floor. The network monitors process parameters, device
parameters, device status, process status and application programs to
support data acquisition, data monitoring, program upload/download
and supervisory control.
The DH-485 network offers:
• interconnection of 32 devices.
• multi-master capability.
• token passing access control.
• the ability to add or remove nodes without disrupting the
network.
• maximum network length of 1219 m (4000 ft).
(1)
The following section describes the protocol used to control message
transfers on the DH-485 network. The protocol supports two classes
of devices: initiators and responders. All initiators on the network get
(1) The network can be extended to 2438 m (8000 ft) by connecting two AIC+ Advanced Interface Converters
(1761-NET-AIC). Refer to the AIC+ Advanced Interface Converter User Manual, publication 1761-UM004.