INVT GD20-0R4G-2-UL, Operation Manual

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Goodrive20-UL Series VFD Communication protocol
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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 high bit is in the front and the low bit is in the
behind.
RTU slave response message (from the VFD to the master)
START T1-T2-T3-T4
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 CHK low bit 7EH
CRC CHK high bit 9DH
END T1-T2-T3-T4
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 CHK
low bit", which are "digital address 0004H high bit", "digital address 0004H low bit", "digital
address 0005H high bit" and "digital address 0005H low bit".
There are 2 bytes stored in one data with the fact that the high bit is in the front and the low bit