Micom P721, Техническое руководство

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Communication database P72x/EN CT/A11
MiCOM P721/P723 Page 7/78
2.5 MODBUS functions of the MiCOM relays
Protection device data may be read or modified by using function codes. Following are the
available function codes. Function codes to read from or write into parameter cells in the
protection device are described in the listed following table.
Function Nr. Data Read Data Write Data Format & Type
1 X N bits
2 X N bits
3 X N words
4 X N words
5 X 1 bit
6 X 1 word
7 Fast 8 bits
8 X Diagnostics counter
11 X Event counter
15 X N bits
16 X N words
2.6 Presentation of the MODBUS protocol
Master slave protocol, all exchange understands a master query and a slave response
Frame size received from MiCOM P721 and P723 relays.
2.6.1 Frame size received by the protection device (slave)
Frame transmitted by the master ( query):
Slave number Function code Information CRC16
1 byte 1 byte n bytes 2 bytes
0 à FFh 1 à 10h
Slave number:
The slave number is situated between 1 and 255.
A frame transmitted with a slave number 0 is globally addressed to all pieces of equipment
(broadcast frame)
Error code:
The MiCOM P72x relays manages the two following error codes:
•
Code 01: the function code is not authorised or is unknown.
•
Code 03: one of the following value from the data field is incorrect:
−
control of data being read,
−
control of data being written,
−
control of data address,
−
length of request for data message.
CRC16:
Value of the CRC16 calculated by the master.
NOTE: The MiCOM relay does not respond to globally broadcast frames sent
out by the master.