Goodrive300-19 series open loop vector inverter special for hosit Communication protocol
-215-
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, read N words (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 stage of the inverter.
For example, read continuous 2 data content from 0004H 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 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
