Danfoss VLT AutomationVTDrive FC322 Design Manual page 221

7 RS-485 Installation and Set-up
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.
Maximum Reference
Example: Read par. 3-03, , register 03030.
Field Name
Slave Address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
Error Check (CRC)
7
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 3030)
Data LO
(Register 3030)
Data HI
(Register 3031)
Data LO
(Register 3031)
Error Check
(CRC)
220
MG.20.X1.22 - VLT
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Automation VT Drive FC322 Design Guide
Example (HEX)
01
03 (read holding registers)
0B (Register address 3029)
05 (Register address 3029)
00
02 - (Par. 3-03 is 32 bits long, i.e. 2 registers)
-
Example (HEX)
01
03
04
00
16
E3
60
-
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