210
The method is advanced with easy program and quick calculation speed. But the ROM
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
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 form 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 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 T1-T2-T3-T4 (transmission time of 3.5 bytes)
ADDR 01H
CMD 03H
High bit of the start bit 00H
Low bit of the start bit 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 (transmission time of 3.5 bytes)
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
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