Danfoss VLT HVAC Drive FC 100 Series Design Manual page 145

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VLT HVAC Drive Design Guide
7.10.4. Read Holding Registers (03 HEX)
Description
This function reads the contents of holding registers in the slave.
Query
The query message specifies the starting register and quantity of registers to be read. Register addresses start at zero, i.e. registers 1-4 are addressed
as 0-3.
Field Name
Slave Address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
Error Check (CRC)
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.
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)
Example (HEX)
01
03 (read holding registers)
00
00 (coil address 17)
00
03
-
Example (HEX)
01
03
06
55
AA
55
AA
55
AA
-
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7. RS-485 Installation and Set-up
7
145