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Connection to a fieldbus
6.4 Communication via RS485
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
131
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Figure 6-11 Communication network via RS485
6.4.2
Communication via USS
6.4.2.1
General information about communication with USS via RS485
Using the USS protocol (protocol of the universal serial interface), users can set up a serial
data connection between a higher-level master system and several slave systems (RS 485
interface). Master systems include programmable logic controllers (e.g. SIMATIC S7-200) or
PCs. The inverters are always slaves on the bus system.
Communication using the USS protocol takes place over the RS485 interface with a
maximum of 31 slaves.
The maximum cable length is 1200 m (3300 ft)
Information about how to connect the inverter to the USS fieldbus is provided in Section:
Integrating inverters into a bus system via the RS485 interface (Page 130).
Setting the bus address of the inverter
The inverter's USS address can be set via DIP switches on the Control Unit or using p2021.
Using p2021, the address can only be set if all DIP switches for the bus address are either
set to "OFF" (0) or to "ON" (127).
If the address switches are set to a value = 1 … 30, then this address is always active and
p2021 is read-only.
Valid USS address area: 1 … 30
The setting using DIP switches is described in Setting the bus address via DIP switch
(Page 104).
CAUTION
A bus address that has been changed is only effective after switching-off and switching-on
again. It is particularly important that any external 24 V supply is switched off.