SIMATIC PCS 7 Process Control System - Siemens

9
Communication
PROFIBUS PA
Introduction
■ Design
Basic PROFIBUS PA design versions when using the DP/PA link as the
router
Basic PROFIBUS PA design versions are presented at this point.
In these configuration examples, DP/PA links are used in each
case as the DP/PA router. Up to 5 DP/PA couplers can be operated
in a DP/PA link. Mixed configurations (e.g. line and ring on
one link) are also possible. The DP/PA router can also be implemented
with a DP/PA coupler. In this case, the PROFIBUS DP
connection is directly on the coupler instead of per interface
module.
Linear architecture with single coupler
In this design version, each PROFIBUS PA line is linked with one
DP/PA coupler of a DP/PA router. Depending on the operating
environment, you can use either the FDC 157-0 DP/PA coupler
(up to Ex zone 2) or the Ex [i] DP/PA coupler (up to Ex zone 1).
The DP/PA router can be connected to a single or redundant
PROFIBUS DP.
Linear architecture with redundant couplers
The active field splitter (AFS) connects a PROFIBUS PA line with
two FDC 157-0 DP/PA couplers of a DP/PA router. This router is
operable on a single or redundant PROFIBUS DP. The AFS
switches the PROFIBUS PA line to the active one of the two redundant
couplers.
Flexible Modular Redundancy is possible at the device level by
grouping individual devices in different PROFIBUS PA lines.
Only one PROFIBUS PA line can be configured with coupler redundancy
on each DP/PA router. A PROFIBUS PA ring cannot
then be operated on this router.
9/44
Direct fieldbus interfacing
PROFIBUS DP
AS 414FH/
AS 417FH
Active field
splitter
DP/PA Link
Active field distributors
PROFIBUS PA
Siemens ST PCS 7 · November 2007
PROFIBUS PA
DP/PA Link
with redundant DP/PA couplers
PROFIBUS PA
DP/PA Link
with redundant DP/PA couplers
© Siemens AG 2007
Ring architecture
Active field distributors (AFD) integrate PROFIBUS PA field
devices via 4 short-circuit proof spur line connections into
a PROFIBUS PA ring with automatic bus termination. The
PROFIBUS PA ring is connected to two FDC 157-0 DP/PA couplers
of a DP/PA router. The DP/PA router can be operated on a
single or redundant PROFIBUS DP. Up to 8 AFDs can be configured
per ring.
Flexible Modular Redundancy is possible at the device level by
grouping individual devices on different AFDs. Only one ring can
be configured on each DP/PA router. A PROFIBUS PA line with
coupler redundancy cannot then be operated on this router.
The following limits must be observed for a PROFIBUS PA ring
with respect to the configuration with PROFIBUS PA devices:
• Max. 31 PROFIBUS-PA devices
• Max. current consumption of all PROFIBUS-PA devices: 1 A
Particular advantages of the ring architecture:
• High availability
• Transparent redundancy management of the intelligent
FDC 157-0 DP/PA couplers for the higher-level system
• Active bus terminations for automatic bus termination in the
FDC 157-0 DP/PA couplers and the AFDs permit:
- Automatic, bumpless isolation of defective sub-segments in
event of short-circuit or wire breakage
- Changing of the ring configuration and the instrumentation
during operation, including addition or removal of ring segments
• Safety-related and fault-tolerant applications with low device
and cabling overheads
■ Technical specifications
PROFIBUS PA
Data transmission MBP
Transmission rate 31.25 Mbit/s
Cable 2-wire shielded
Type of protection EEx(ia/ib)
Topology Line, tree, ring
PA devices per segment/coupler 31
PA devices per DP/PA link 64
Cable length per segment depen- 1900 m: standard
dent on transmission rate
1900 m: EEx(ib)
1000 m: EEx(ia)