Fundamentals of PROFIBUS-PA
A-4
DP/PA Link and Y Link Bus Couplings
A5E00193841-011
A.3 Extending PROFIBUS-PA with the DP/PA link coupler
Extension
The figure below shows the configuration of a PROFIBUS-PA system with a DP
master:
DP master
Max. 5 DP/PA
couplers per
IM 157
Max. 64 PA
field devices
per DP/PA link
DP master
Max. 31 PA field
devices per
DP/PA coupler
Configuration with a DP/PA link Configuration with DP/PA couplers
Figure A-2 Extension of PROFIBUS-PA with a DP/PA link or DP/PA couplers
Rules
The following rules apply to PROFIBUS-PA extensions:
There can be no more than 31 PA field devices in a physical PROFIBUS-PA
segment.
Not more than one supply device (= DP/PA coupler) can be connected in one
physical PROFIBUS-PA segment.
No more than 64 PA field devices can be connected to a DP/PA link. The
maximum number of PA field devices that can be connected in each physical
PROFIBUS-PA segment and each DP/PA coupler is limited by the maximum
output current of the DP/PA coupler and the I/O data to be transferred (see
Appendix B).
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