IMO SD1 Series - Page 128

SD1 Series Inverters Communication Protocol
-123-
ADDR
01H
CMD
03H
High bit of the start address
00H
Low bit of the start address
04H
High bit of data number
00H
Low bit of data number
02H
CRC low bit
85H
CRC high bit
CAH
END
T1-T2-T3-T4
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 from the inverter 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 high bit in the front and the low bit in the behind.
RTU slave response message (from the inverter 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 inverter with the address of 01H