Operating instructions

VLT
®
2800, VLT
®
6000 HVAC and VLT
®
8000 AQUA Modbus RTU
Supported Modbus RTU
Function Codes
Query
The query message specifies the coil references
to be forced. Coils are addressed starting at
zero. Coil 1 is addressed as 0.
See example 1 Start Motor, Run Speed 40 %.
Field Name Example (HEX)
Slave Address 01
Function 0F
Coil Address HI 00
Coil Address LO 00
Quantity of Coils HI 00
Quantity of Coils LO 0A
Byt Count 02
ForceDataHI(Coils
8-1)
FF
Force Data LO (Coils
10-9)
03
Error Check (CRC) -
Response
The normal response returns the slave address, function
code, starting address, and quantity of coils forced.
Field Name Example (HEX)
Slave Address 01
Function 0F
Coil Address HI 00
Coil Address LO 00
Quantity of Coils HI 00
Quantity of Coils LO 0A
Error Check (CRC) -
■ Read Holding Registers (03
HEX
)
Description
Reads the binary contents of holding registers
(4x references) in the slave. Broadcast is
never supported for reads.
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.
See example 4 Write Parameter 104, Motor Frequency.
Field Name Example (HEX)
Slave Address 01
Function 03
Starting Address HI 00
Starting Address LO 00
No. of Points HI 00
No. of Points LO 03
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 second contains the low order bits.
Field Name Example (HEX)
Slave Address 01
Function 03
Byte Count 06
Data HI (Register
40001)
55
Data LO (Register
40001)
AA
Data HI (Register
40002)
55
Data LO (Register
40002)
AA
Data HI (Register
40003)
55
Data LO (Register
40003)
AA
Error Check (CRC) -
■ Preset Single Register (06
HEX
)
Description
Presets a value into a single holding register (4x
reference). When broadcast, the function presets the
same register reference in all attached slaves.
Query
The query message specifies the register reference
to be preset. Registers are addressed starting at
zero. Register 1 is addressed as 0.
See example 4 Write Parameter 104, Motor Frequency.
MG.10.S2.02 - VLT is a registered Danfoss trademark
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