Astraada DRV-24 frequency inverters Communication protocol
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High bit of the start address
Low bit of the start address
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 behind.
RTU slave response message (from the inverter to the master)
Data high bit of address
0004H
Data low bit of address
0004H
Data high bit of address
0005H
Data low bit of address
0005H
The meaning of the response is that:
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 message is received from the inverter to the master for the response of
reading command and CMD occupies one byte
“Byte number” means all byte number from the byte(excluding the byte) to CRC byte(excluding the
byte). 04 means there are 4 byte of data from the “byte number” to “CRC CHK low bit”, which are
“digital address 0004H high bit”, “digital address 0004H low bit”, “digital address 0005H high bit”
and “digital address 0005H low bit”.
There are 2 bytes stored in one data with the fact that the high bit is in the front and the low bit is in
the behind of the message, the data of data address 0004H is 1388H,and the data of data address
0005H is 0000H.
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