Iec 61158 Data Highway And Connections; Data Highway - rotork Mk3 Technical Manual

4

IEC 61158 DATA HIGHWAY AND CONNECTIONS

4.1

Data highway

The Foundation Fieldbus network is based on the IEC 61158 data highway using copper conductors.
The network also carries the power used to supply each node on the network. In the case of the FF
card, the FF interface is powered from the fieldbus network. Only two wires are used for the data
highway and these carry both the data signal and the module power. The actuator interface card is
powered from the actuator itself and the card can only report actuator data when both the FF highway
and actuator are powered up.
Fieldbus power supply
(including terminator)
Power
supply
Fig 4.1: Typical Foundation Data Highway
The data highway must be terminated with proper balancing devices at either end. The highway can
use spur or stub connections to the devices but it is recommended to keep any stub lengths to a
minimum for successful operation. The length of the highway and number of devices connected will
vary from project to project. The standard permits up to 32 devices before a repeater in the highway
must be used, however it's extremely unlikely that this many devices will be connected to a highway.
Similarly, the standard calls for a maximum segment length of 1900 metres before a repeater must be
used. On a 1900 metre highway, the stipulated maximum length for a stub with one actuator is 120
metres. The data highway cable type is given by the Foundation as 'type A'. A typical example of this
type of cable is Belden 3076F.
Cable Specification
Type
Shielding
Size
Resistance
Nominal Capacitance
H1 Gateway
T
Publication PUB089-005-00_0618
Trunk
(Main highway segment)
JB
Type A Cable (e.g. Belden 3076F)
2 cores, twisted pair plus overall screen
Minimum 90% copper shielding, braid or foil
2
18 AWG (0.8 mm )
24 Ohms/km max
80 pF/m
IEC 61158 Data Highway
Field Junction Box
(including terminator)
T
Spurs
JB
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