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UMI-B1 UL Series Inverter
7.3 RTU command code and communication data illustration
7.3.1 Command code: 03H
03H (correspond to binary 0000 0011), read N words (Word) (the Max. continuous
reading is 16 words)
Command code 03H means that if the master read data from the inverter, the reading
number depends on the "data number" in the command code. The 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 stage 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 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 fact that the high bit is in the front and the low bit is in the
T1-T2-T3-T4
01H
03H
00H
04H
00H
02H
85H
CAH
T1-T2-T3-T4
115
Communication protocol
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