Configuration Manual Owner manual

Publication 1757-PM002A-EN-E - June 2006

Set Up A System 2-25

However, it is still best to call RA Tech Support (see page 1-6) if this situation

occurs, and for other problems concerning DHCP.

H1 Fieldbus is a digital, serial, multidrop data bus for communication with

industrial devices or systems. The Physical Layer provides for transparent

transmission of data between Data Link Layer entities across physical

connections.

The Physical Layer receives data from the Data Link Layer, adds preamble and

delimiters, provides encoding and transmits the resulting physical signals to the

wire medium. Signals are then received at one or more other devices and

decoded and stripped of preamble and delimiters before being passed to the

Data Link Layer of the receiving device(s).

Figure ?.?? shows a physical realization of a simple H1 network using Relcom

physical media. Please note that the RelCom FCS-PCT2 incorporates two (2)

terminators. The power supply may be any good 24 VDC supply that meets

the current requirements for the number of devices. Additional FCS-Es could

be added if more devices are added to the network.

Device Addressing

When installing instruments for the first time, it is recommended that each

instrument be installed one at a time and that you address the instruments in

succession (one after the other). Because like instruments have the same H1

foundation fieldbus address from the factory, you will only be able to see one

device. This condition will disable the installer from knowing which device he

is actually programming in the plant.

Also, the installer must decide which address to start with for each H1 node.

Currently, the linking device (address 10) addresses devices consecutively

starting at 18. Other Rockwell Interfaces, like the CN2FF (address 16), starts

numbering at 17. The FIM starts numbering at address 18.

Number of Devices per H1 Segment

The specified number of devices per H1 is 32. However, it should be noted

that most manufacturers would agree that the actual maximum limit to the

number of devices on the H1 is approximately 16. This is due to voltage drop

and the physical media that the system uses.

Rockwell Automation feels that the H1’s design is optimized by having 6 to 8

devices per H1 network. This optimized limit is mainly due to physical media,

the time required for each device to communicate, the extra bandwidth