Siemens MICROMASTER 420 - Fig. 3-30 RS485 Terminator; USS Bus Configuration Via COM Link (RS485)

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3 Functions Issue 07/04

MICROMASTER 420 Operating Instructions

98 6SE6400-5AA00-0BP0

3.7.1 USS bus configuration via COM link (RS485)

Using MICROMASTER with RS485 communication requires a proper termination

both ends of the bus (between P+ and N-), and correct pull up/ pull down

resistors at least one end of the bus (e.g. from P+ to P10, and N- to 0 V). (refer to

Fig. 3-30)

Fig. 3-30 RS485 Terminator

When the MICROMASTER drive inverter is the last slave on the bus (refer to Fig.

3-31), and there are no other pull up/pull down resistors on the bus, the supplied

terminator must be connected shown in Fig. 3-30).

First Slave

Last Slave

RS485 Terminator

RS485

Terminator

RS485 Bus

Master

e.g. PLC

Fig. 3-31 USS bus configuration

When the MICROMASTER is the first slave on the bus (refer to Fig. 3-31) the

RS485 Terminator may be used to terminate the bus by using P+ and N- only, for

the bus is powered by the last drive as explained.

NOTE

The supply for the pull up/ pull down resistors must be available whenever RS485

communication is in progress!

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