Areva MiCOM P225, Technical Manual

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P225/EN CT/B11 Communication
Page 4/52 MiCOM P225
1.1.2 Parameters of the MODBUS connection
The different parameters of the MODBUS connection are as follows :
−
Isolated two-point RS485 connection (2kV 50Hz).
−
MODBUS line protocol in RTU mode.
−
The baud rate can be configured by operator dialogue in the front panel of the relay :
Baud rate
300
600
1200
2400
4800
9600
19200
38400
−
Transmission mode of the configurable parameters by operator dialogue :
Transmission mode
1 start / 8 bits / 1 stop : total 10 bits
1 start / 8 bits / even parity / 1 stop : total 11 bits
1 start / 8 bits / odd parity / 1 stop : total 11 bits
1 start / 8 bits / 2 stop : total 11 bits
1.1.3 Synchronisation of exchange messages
Any character received after a silence on the line with more or equal to a transmission time
of 3 bytes is considered as a frame start.
1.1.4 Message validity check
The validation of a trame is performed with a 16-bit cyclical redundancy check (CRC). The
generator polynomial is :
1 + x² + x
15
+ x
16
= 1010 0000 0000 0001 binary = A001h
1.1.5 Address of the MiCOM relays
The address of the MiCOM relay on a same MODBUS network is situated between 1 and
255. The address 0 is reserved for the broadcast messages.