Hardware Style Owner's manual

A
Appendix
A–1
Setting Up the DH-485 Network
The information in this appendix will help you plan, install, and operate the
SLC 500 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
• example system configuration
• important planning considerations
• DH–485 network installation
We have designed the DH–485 network to pass 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)
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 a chance
to initiate message transfers. To determine which initiator has the right to
transmit, a token passing algorithm is used.
DH-485 Network Description
DH-485 Network Protocol