SIEMENS
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Siemens IK PI · 2015
PROFIBUS
Network transistions
PA routers
3
■
Overview
To create a smooth network transition between PROFIBUS DP
and PROFIBUS PA, the SIMATIC product range offers two
versions: the DP/PA coupler and the PA link.
The following criteria can be applied when choosing the network
transition:
• DP/PA coupler:
For small quantity frameworks (volumes of data) and low
timing requirements; limiting of data transfer rate on the
PROFIBUS DP to 45.45 kbit/s
•
PA link:
For large number of stations and high cycle time require-
ments; data transfer rate on the PROFIBUS DP up to 12 Mbit/s
■
Application
The two PA routers are based on two versions of the
DP/PA coupler:
•
Ex [i] DP/PA coupler (max. output current 110 mA)
for implementation of PROFIBUS PA networks with a line or
tree topology in environments up to Ex zone 1/21, not for
redundant architectures (coupler redundancy, ring)
•
FDC 157-0 DP/PA coupler (max. output current 1 000 mA)
for implementation of PROFIBUS PA networks with a line, tree
or ring topology in environments up to Ex zone 2/22; can be
used for the redundant architectures "Ring" and "Coupler
redundancy"
DP/PA couplers are also integral components of the PA link (see
design). The PA
link connects PROFIBUS
DP and PROFIBUS
PA
together, and decouples the transmission rates. In contrast to
the DP/PA coupler which limits the data transmission rate on the
PROFIBUS DP to 45.45 kbit/s, the PA link does not influence the
performance of the PROFIBUS DP.
The PA link functions as a slave on the PROFIBUS DP and as a
master on the PROFIBUS PA. From the viewpoint of the host
PROFIBUS DP master, the PA link is a modular slave whose
modules are the devices connected on the PROFIBUS PA.
Addressing of these devices is carried out indirectly via the
PA link that itself only requires one node address. The host
PROFIBUS master can scan devices connected to the PA link all
at once.
If the router is a DP/PA coupler, the nodes on the PROFIBUS PA
are directly addressed by the PROFIBUS DP master (controller).
The DP/PA coupler is an electrical node, but is transparent for
communication between the master and PA field devices; it
therefore does not require setting of parameters or addresses
(exception: FDC 157-0 DP/PA coupler used as PROFIBUS
diagnostics slave).
PROFIBUS diagnostics with FDC 157-0 DP/PA coupler,
configured as PROFIBUS diagnostics slave
FDC 157-0 DP/PA couplers configured as PROFIBUS diagnos-
tics slaves supply extensive diagnostic and status information
via PROFIBUS for swift localization and correction of faults:
•
I&M (Identification & Maintenance) data
•
Current and voltage values on the main cable
•
Redundancy status
•
Wire breakage
• Short-circuit
•
Signal level
To this end, each of these DP/PA couplers FDC 157-0 requires
its own PROFIBUS address. This applies independent of use in
a PA Link or as a PA router.
The PA link and DP/PA coupler approved for an extended
temperature range are available for use in environments up to
Ex zone 2/22. Both are operated with 24 V DC. Assembly is on
an S7-300 rail with horizontal or vertical alignment.
© Siemens AG 2014