Rtu Command Code And Communication Data Illustration; Command Code: 03H; Rtu Master Command Message (From The Master To The Inverter) - INVT GD200-037G/045P-4 Operation Manual

Goodrive200 inverters
space the program occupied is huge. So use it with caution according to the program
required space.

10.4 RTU command code and communication data illustration

10.4.1 Command code: 03H

read N words（Word）(the Max. continuous reading is 16 words)
Command code 03H means that if the master read data form the inverter, the reading
number depends on the "data number" in the command code. Max. continuous reading
number is 16 and the parameter address should be continuous. The byte length of every
data is 2 (one word). The following command format is illustrated by hex (a number with "H"
means hex) and one hex occupies one byte.
The command code is used to read the working step of the inverter.
For example, read continuous 2 data content from0004H from the inverter with the address
of 01H (read the content of data address of 0004H and 0005H), the frame structure is as
below:

RTU master command message (from the master to the inverter)

START
ADDR
CMD
High bit of the start address
Low bit of the start address
High bit of data number
Low bit of data number
CRC low bit
CRC high bit
END
T1-T2-T3-T4 between START and END is to provide at least the time of 3.5 bytes as the
leisure time and distinguish two messages for the avoidance of taking two messages as one
message.
ADDR = 01H means the command message is sent to the inverter with the address of 01H
and ADDR occupies one byte
CMD=03H means the command message is sent to read data form the inverter and CMD
occupies one byte
"Start address" means reading data form the address and it occupies 2 bytes with the fact
T1-T2-T3-T4 (transmission time of 3.5 bytes)
CAH
T1-T2-T3-T4 (transmission time of 3.5 bytes)
224
Communication protocol
01H
03H
00H
04H
00H
02H
85H