Danfoss Modbus RTU Manual page 28

Description
Read
Reads the binary contents of holding registers
Holding
(4x references) in the slave. Broadcast is never
Registers
supported for reads.
(03 )
HEX
Query
The query message specifies the starting
register and quantity of registers to be read.
Registers are addressed starting at zero.
Registers 1-4 are addressed as 0-3.
Example of a request to read registers 40001-03 from slave device 01.
Response
The register data in the response message
are packed as two bytes per register, with the
binary contents right justified within each byte.
For each register, the first byte contains the
high order bits and the second contains the
low order bits.
28
Field Name
Slave Address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
Error Check (CRC)
Field Name
Slave Address
Function
Byte Count
Data HI (Register 40001)
Data LO (Register 40001)
Data HI (Register 40002)
Data LO (Register 40002)
Data HI (Register 40003)
Data LO (Register 40003)
Error Check (CRC)
APPENDIX A
MG.10.P2.22
Example (HEX)
01
03
00
00
00
03
–
Example (HEX)
01
03
06
55
AA
55
AA
55
AA
–
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