Siemens SIMATIC NET PROFIBUS Owner's Manual page 52

Topologies of SIMATIC NET PROFIBUS Networks
Properties
The DP/PA link has the following characteristics:
S Diagnostics with LEDs and the user program
S DP slave and PA master
S Can be operated at all transmission rates (9.6 Kbps to 12 Mbps)
S Only DP/PA couplers can be operated with an IM 157
How the DP/PA Link Works
Figure 2-17 shows how the DP/PA link with the IM 157 and the DP/PA couplers
functions.
S The DP/PA link maps the underlying PROFIBUS-PA system on a DP slave.
S With the DP/PA link, PROFIBUS-DP is completely isolated from
PROFIBUS-PA.
S The PA master and PA slaves form a separate, underlying bus system.
S The number of DP/PA couplers simply reflects the amount of current required.
All DP/PA couplers along with the attached PA field devices form one common
PROFIBUS-PA bus system.
DP/PA Link
Figure 2-17
2-26
DP
DP slave
IM 157
S7 backplane bus
DP/PA coupler
(max. 5)
The DP/PA Link with DP/PA Couplers
PA master
PA
PA
PA PA
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000