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daqmaster
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Joined: 27 Jun 2005
Posts: 385
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 Posted: Wed Jul 06, 2005 7:16 am Post subject: Data Highway Plus Network |
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Data Highway Plus Network (DH+) is probably the most common (popular) industrial and plant-automation networking architecture in world. What exactly is it comprised of? Below is Allen-Bradley's overview and specs on DH+:
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The Data Highway Plus (DH+) network is a local area network that is very simple to implement. It is designed to provide simple communication between PLCs, SLCs and PCs.
Product Design
The Data Highway Plus network allows connection to a maximum of 64 devices per link (although 15 or fewer nodes are recommended per link), including:
* PLC-5 and SLC 5/04 programmable controllers
* Color graphics systems
* Personal computers
* Host computers
* Numerical controls
* Programmable RS-232-C/RS-422 devices
A network can be configured with 99 links. With a multi-link network, more nodes in the network are possible. By placing nodes in the proper link with some nodes and separate from other nodes, the efficiency of message delivery can be improved. Using simple twisted-pair wiring, DH+ can be configured as a trunk-line drop or a daisy-chain topology.
Communication
Use Rockwell Software Programming Software to program the PLC controllers over the Data Highway Plus network, or program a PLC controller from its local DH+ link or from a remote DH+ link in the network. This means that a single industrial terminal connected to the network can be used to program all the PLC controllers on all links of the network.
The ControlLogix Communication Interface Module (1756-DHRIO) interfaces two DH+ links to the ControlLogix backplane to provide routing of messages between a DH+ link and EtherNet/IP, ControlNet, DeviceNet, and other DH+ links.
Data Highway Plus modules can also be used to implement a SCADA network.
Benefits
* Includes switches on each interface that make it easy to reconfigure the network as it changes.
* Incorporates network diagnostics that help the user avoid costly downtime and improve network efficiency.
* Allows for use of communication software to provide a Data Highway Plus communication driver to various computer platforms.
Cabling (1770-CD shielded twinaxial):
trunkline - 10,000 ft max.
droplines - 100 ft max.
Transmission Characteristics:
token passing
57.6 kbit/s
230 kbit/s on selected products
Operating Temperature:
1770-KF2: 0
50 °C (32
122 °F)
all other Data Highway Plus backplane-resident modules: 0
60 °C (32
140 °F)
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