Nidec LEROY-SOMER Powerdrive FX, Commissioning Manual

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167
OPERATION WITH MODBUS RTU
Commissioning manual Powerdrive MD2/FX
4617 en - 2017.09 / e
6.4.6 - Example
Drive address = 1 (Default address).
Reading of 3 drive parameters from 1.05 .
1.05 becomes 1.04 which is equal to 68 in hexadecimal (Modbus address = drive parameter address - 1).
• Request
Example (hex) RTU (binary)
Slave address 1 0000 0001
Function 03 0000 0011
Start word or register address (MS byte) 00 0000 0000
Start word or register address (LS byte) 68 0110 1000
Number of words or registers (MSB) 00 0000 0000
Number of words or registers (LSB) 03 0000 0011
CRC check: LS byte 84 1000 0100
MS byte 17 0001 0111
Total bytes: 8
• Response
Example (hex) RTU (binary)
Slave address 1 0000 0001
Function 03 0000 0011
Number of bytes 06 0000 0110
Word or register 0 (MS byte) 00 0000 0000
Word or register 0 (LS byte) 2D 0010 1101
Word or register 1 (MS byte) 05 0000 0101
Word or register 1 (LS byte) DC 1101 1100
Word or register 2 (MS byte) 00 0000 0000
Word or register 2 (LS byte) 00 0000 0000
CRC check: LS byte 4C 0100 1100
MS byte 45 0100 0101
Total bytes 11
• Function code 23: Read/write
Writes and reads two contiguous arrays of registers. The slave
imposes an upper limit on the number of registers which can be
written. If the limit is exceeded, the slave does not respond.
Note: 99 parameters maximum can be read and 10 parameters
maximum can be written.
Frame sent by the Master:
Bytes Description
0 Slave address (1 to 247)
1 Function code 0x17
2 Start word to be read address MS byte
3 Start word to be read address LS byte
4 Number of words to be read MS byte
5 Number of words to be read LS byte
6 Start word to be written address MS byte
7 Start word to be written address LS byte
8 Number of words to be written MS byte
9 Number of words to be written LS byte
10 Number of bytes to be written
11 Word 0 MS byte
12 Word 0 LS byte
13 Word 1 MS byte
14 Word 1 LS byte
... …
n CRC LS byte
n + 1 CRC MS byte
Where n = 11 + number of bytes to be written.
Frame returned by the slave:
Bytes Description
0 Slave address (1 to 247)
1 Function code 0x17
2 Number of bytes to be read
3 Word 0 MS byte
4 Word 0 LS byte
5 Word 1 MS byte
6 Word 1 LS byte
... …
n CRC LS byte
n + 1 CRC MS byte
Where n = 3 + number of bytes to be read.