Siemens Server - Manual (Page 13)

Connecting more than one ChemWeb Server
7
For these resistors, the followings values are recommended:
R
t
150 Ohm +/- 2 % min. 0.25 W
R
u
390 Ohm +/- 2 % min. 0.25 W
R
d
390 Ohm +/- 2 % min. 0.25 W
The interface lines are named as line A and line B. Each RS485 bus user is equipped with an interface
for the connection of these lines.
Due to the different enclosure protection classes, the bus connections of the devices vary. The bus
cable can be connected to the bus users via terminals or 9-pole DSUB plug connectors.
Bus connection and parameterization of the process hardware
The individual process devices (bus users) must be parameterized properly for the connection to the
bus. Furthermore the devices have different bus connections. For details, please refer to the operating
instructions of the devices concerned.
When setting up the bus system, attention must be paid to the assignment of the bus addresses of the
process devices. Each bus user must have a different bus address. If the same bus address is assigned
to two or more bus users, the ChemWeb Server is unable to establish a communication. The
ChemWeb Server is the master of the RS485 bus and therefore does not occupy a bus address.