Installing • Commissioning
7
RS-485 Repeaters
If more than 32 stations are connected to the bus, the signals on
the bus have to be amplified by RS-485 repeaters. -
Note that one repeater is needed for every 31 stations (master
plus slaves), since the RS-485 repeater itself is to be considered
as a bus station as well.
Every section up to the first repeater or between two repeaters is
called a bus segment. -
Repeaters are also required if a bus segment needed for the
respective application cannot be realized using the possible cable
lengths (given by the baud rate). - Refer to the RS-485 repeater
documentation for the possible cable lengths.- The max. number
of RS-485 repeaters that can be connected in series is also
specified in these manuals. -
Since RS-485 repeaters are usually the first or last station in a
bus network, they must be provided with the respective
termination resistors to terminate the bus properly.
Station address
The station address of the device, i.e. of a DP slave on a
communication bus, is entered in the controller list configuration
under Device/Communication/Functional block 30/DP
address/Inquiry 06.-- Any number between 1 and 125 is a valid
entry. Automatic address assignment through the master is not
supported.- This inquiry can only be selected with the device
firmware revisions for library 3.5.0. The other inquiries in
functional block 30 are used for setting up the communication via
the RS-232 and RS-485 interface modules.
Additional recommendations related to installation and configuration
During the commissioning phase it may become necessary to
increase the storage areas for the input and output data due to
additional variables. Therefore, it is recommended to reserve a
bigger area already when making the slave-specific configuration.
Then it is only necessary to change the slave-specific parameter
settings.
It is not always possible to write on the variable indices while the
device is working. When the device is in configuration mode
(menu level 2) in the menu system, the index can be written, but
the PROFIBUS-DP module does not transmit the value to the
device.-
Lateral Communication
If an optional RS-232 or RS-485 interface module has been
installed in the controller, lateral communication programmable
within the free configuration can be run in parallel with
PROFIBUS-DP communication. - The necessary communication
parameters have to be set by answering the inquiries of functional
block 30 in the device configuration, dedicated to lateral
communication.
Lateral communication has been configured in such a way that
simultaneous writing on variables via lateral communication and
PROFIBUS-DP communication is not possible. ---Therefore, no
special attention has to be paid to a possible interlocking of these
two functions. -
