Goodrive3000 series medium voltage VFD MODBUS protocol
-252-
ADDR=01H means the command message is sent to the VFD with the address of 01H and ADDR
occupies one byte;
CMD=03H means the command message is sent to read data from the VFD and CMD occupies one
byte;
"Start address" means reading data from the address and it occupies 2 bytes with the fact that the high bit
is in the front and the low bit is in the behind.
"Data number" means the reading data number with the unit of word. If the "start address" is 0004H and
the "data number" is 0002H, the data of 0004H and 0005H will be read.
CRC occupies 2 bytes with the fact that the low bit is in the front and the high bit is in the behind.
RTU slave response message (from the VFD to the master)
START
T1-T2-T3-T4 (transmission time of 3.5 bytes)
ADDR
01H
CMD
03H
Byte number
04H
Data high bit of address 0004H
13H
Data low bit of address 0004H
88H
Data high bit of address 0005H
00H
Data low bit of address 0005H
00H
CRC low bit
7EH
CRC high bit
9DH
END
T1-T2-T3-T4 (transmission time of 3.5 bytes)
The meaning of the response is that:
ADDR=01H means the command message is sent to the VFD with the address of 01H and ADDR
occupies one byte;
CMD=03H means the message is received from the VFD to the master for the response of reading
command and CMD occupies one byte;
"Byte number" means all byte number from the byte (excluding the byte) to CRC byte (excluding the byte).
04 means there are 4 byte of data from the "byte number" to "CRC low bit", which are "digital address
0004H high bit", "data low bit of address 0004H", "data high bit of address 0005H" and "data low bit of
address 0005H".
There are 2 bytes stored in one data with the fact that the high bit is in the front and the low bit is in the
behind of the message, the data of address 0004H is 1388H, and the data of address 0005H is 0000H.
CRC occupies 2 bytes with the fact that the low bit is in the front and the high bit is in the behind.
8.4.2 Command code: 06H, write one word
The command means that the master write data to the VFD and one command can write one data other
than multiple data. The effect is to change the working mode of the VFD.
