Siemens SITRANS T3K PA Instruction Manual page 109

Instruction Manual 7NG3213
Master Master
(class 1) (class 2)
PROFIBUS-DP
PROFIBUS-PA
I
Slaves
(field devices, decentral peripheral, cascaded con-
trol systems, mains transition to PROFIBUS-PA)
Figure 7 Typical PROFIBUS automation system
Figure 7 shows the section of a typical PROFIBUS automation system. The con-
trol system consists of two masters with distributed tasks.
The master class 1 looks after the control and regulation functions, master class 2
enables operating and monitoring functions. A cyclic exchange of measing and
setting data takes place between master 1 and the field devices. Parallel to these
data the status data of the field devices are evaluated in master class 1. Para-
meterization of the field devices or reading of further device information does not
take place in cyclic operation.
The information necessary for setting up communication is in the control system
through the stored, device-specific device data file GSD (see appendix 2, page
115, "Device data file").
In addition to cyclic operation, one or more class 2 masters have acyclic access to
the field devices. Further informtion can be obtained from the devices or settings
made in the devices with this type of communication.
SITRANS T3K PA
109
C79000-B7174-C55-04