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10-1 Modbus RTU
The VSD provides possibility for different types of serial communication:
•
Modbus RTU via RS232/485
•
Fieldbuses as Profibus DP and DeviceNet
•
Industrial Ethernet type Modbus/TCP and EtherCAT
The VSD has an asynchronous serial communication interface behind the
control panel. The protocol used for data exchange is based in the Modbus
RTU protocol, originally developed by Modicon. the physical connection is
RS232. The VSD acts as a slave with address 1 in a master-slave configura-
tion. The communication is half-duplex. It has a standard no return zero (NRZ)
format.
The baud rate is fixed to 9600.
The character frame format (always 11 bits) has:
•
One start bit
•
Eight data bits
•
Two stop bits
•
No parity
It is possible to temporarily connect a personal computer with for example the
software EmoSoftCom (programming and monitoring software) to the RS232
connector on the control panel. This can be useful when copying parameters
between variable speed drives etc. For permanent connection of a personal
computer you have to use one of the communication option boards.
Note This RS232 port is not isolated.
Note Correct and safe use of a RS232 connection depends on the ground pins of
both ports being the same potential. Problems can occur when connecting
two ports of e.g. machinery and computers where both ground pins are not
the same potential. This may cause hazardous ground loops that can destroy
the RS232 ports.
Note The control panel RS232 connection is not galvanic isolated.
Note The optional RS232/485 card is galvanic isolated.
Note Note that the control panel RS232 connection can safely be used in
combination with commercial available isolated USB to RS232 converters.
SECTION 10
Serial communication
77
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