Siemens CBP Manual Del Usuario página 71

CBP/CBP2 – Communication Board PROFIBUS
Data exchange via
PROFIBUS
PROFIBUS telegram
2-2
The bus system enables very fast transfer of data between higher-level
systems (e.g. SIMATIC, SIMADYN D, PC/PGs) and the drives. Access
to the drives is made in the bus system according to the master-slaves
method. The drives are always the slaves and each slave is clearly
defined by its address.
MASTERDRIVES
Higher-level
computer
"Master"
PROFIBUS interface (PROFIBUS cable)
Fig. 2-2 PROFIBUS connections
Data is exchanged via telegrams. Useful data are transferred in each
telegram which can be divided up into two groups:
♦ 1.
Parameters (parameter identifier value, PKW)
♦ 2.
Process data (PZD)
Protocol frame
Parameters
(Header)
1) PKW: Parameter identifier value
Fig. 2-3 Structure of useful data in the PROFIBUS DP telegram
In the PKW area, all data intended for reading or writing parameter
values and for reading parameter characteristics are transferred.
In the PZD area, all information necessary for guiding a variable-speed
drive is transferred. Control information (control words) and setpoints
are given to the slaves by the PROFIBUS DP master. Information on
the status of the slaves (status words) and actual values are transferred
in the reverse direction.
The length of the PKW and PZD data portions in the telegram is
determined by the master. The master also specifies the baud rate.
Only the bus address and, if necessary, the telegram failure time are
set on the slave.
Other
"Slave"
"Slave"
CBP
Useful data
Process data
1)
(PKW) (PZD)
6SE7087-6NX84-0FF5
Option boards
06.2005
Other
nodes
Protocol frame
(Trailer)
Siemens AG
SIMOVERT MASTERDRIVES