INVT Goodrive270 Series Operation Manual page 310

Goodrive270 series VFD for fan and pump
START
ADDR (address)
CMD (command code)
Start address MSB
Start address LSB
Data count MSB
Data count LSB
CRC LSB
CRC MSB
END
The value in START and END is "T1-T2-T3-T4 (transmission time of 3.5 bytes)", indicating that the
RS485 needs to stay idle for at least the transmission time of 3.5 bytes. An idle time is required to
distinguish on message from another to ensure that the two messages are not regarded as one.
"ADDR" is "01H", indicating that the command is sent to the VFD whose address is 01H. The ADDR
information occupies one byte.
"CMD" is "03H", indicating that the command is used to read data from the VFD. The CMD
information occupies one byte.
"Start address" means reading data from the address and it occupies two bytes with the MSB on the
left and LSB on the right.
"Data count" indicates the count of data to be read (unit: word). "Start address" is "0004H" and "Data
count" is 0002H, indicating that data is to be read from the data addresses of 0004H and 0005H.
CRC check occupies two bytes, with the LSB on the left, and MSB on the right.
RTU slave response (from the VFD to the master)
Number of bytes
MSB of data in 0004H
LSB of data in 0004H
MSB of data in 0005H
LSB of data in 0005H
The definition of the response information is described as follows:
START
ADDR
CMD
CRC LSB
CRC MSB
END
T1-T2-T3-T4 (transmission time of 3.5 bytes)
CAH
T1-T2-T3-T4 (transmission time of 3.5 bytes)
T1-T2-T3-T4 (transmission time of 3.5
T1-T2-T3-T4 (transmission time of 3.5 bytes)
-300-
Communication protocol
01H
03H
00H
04H
00H
02H
85H
bytes)
01H
03H
04H
13H
88H
00H
00H
7EH
9DH