Examples - Danfoss VLT AQUA Drive Design Manual

7. RS-485 Installation and Set-up
7.9.5. Conversion Factor
The different attributes for each parameter can be seen in the section on factory settings. Since
a parameter value can only be transferred as a whole number, a conversion factor must be used
to transfer decimals. Please refer to the
7.9.6. Parameter Values
Standard Data Types
Standard data types are int16, int32, uint8, uint16 and uint32. They are stored as 4x registers
(40001 – 4FFFF). The parameters are read using function 03HEX "Read Holding Registers." Pa-
rameters are written using the function 6HEX "Preset Single Register" for 1 register (16 bits), and
the function 10HEX "Preset Multiple Registers" for 2 registers (32 bits). Readable sizes range from
1 register (16 bits) up to 10 registers (20 characters).
Non standard Data Types
Non standard data types are text strings stored as 4x registers (40001 – 4FFFF). The parameters
are read using function 03HEX "Read Holding Registers" and written using function 10HEX "Preset
Multiple Registers." Readable sizes range from 1 register (2 characters) up to 10 registers (20
7
characters).

7.10. Examples

The following examples illustrate various Modbus RTU commands. If an error occurs, please refer
to the Exception Codes section.
7.10.1. Read Coil Status (01 HEX)
Description
This function reads the ON/OFF status of discrete outputs (coils) in the adjustable frequency drive.
Broadcast is never supported for reads.
Query
The query message specifies the starting coil and quantity of coils to be read. Coil addresses start
at zero, i.e., coil 33 is addressed as 32.
Example of a request to read coils 33-48 (Status Word) from slave device 01:
Field Name
Slave Address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
Error Check (CRC)
142
Parameters section
Example (HEX)
01 (adjustable frequency drive address)
01 (read coils)
00
20 (32 decimals)
00
10 (16 decimals)
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