Operating instructions

VLT
®
2800, VLT
®
6000 HVAC and VLT
®
8000 AQUA Modbus RTU
■ Parameter Handling
■ Parameter Handling
PNU (Parameter Number) is translated from the
register address contained in the Modbus read/write
message. The parameter number is translated to
Modbus as (10 x parameter number)
DECIMAL
.
■ Storage of Data
Coil 65 decimal determines whether data written to
the frequency converter are stored in EEPROM and
RAM (coil 65 = 1) or just RAM (coil 65 = 0).
■ IND
Array index is set in Holding Register 9 and used
when accessing array parameters in the frequency
converter such as parameter 606-617 (Logs).
■ Text Blocks
Parameters stored as text strings are accessed in the
same way as the other parameters. The maximum
text block size is 20 characters. If a read request for a
parameter is for more characters than the parameter
stores, the response is space filled. If the read
request for a parameter is for less characters than the
parameter stores, the response is truncated.
■ PCD
1
/PCD
2
PCD contains the process word block. The parameter
value block consists of 2 words (4 bytes). The process
word block is divided into two blocks of 16 bits and
is stored in Modbus as status coils. The map
ping
of the PCD is shown in the table below.
■ Conversion Factor
The different attributes for each parameter can be seen
in the section on factory settings. Si
nce a parameter
value can only be transferred as a whole number, a
conversion factor must be used to transfer decimals.
Parameter 201: Minimum Frequency,conversion
factor 0.1. If parameter 201 is
to be set to 10
Hz, a value of 100 must be transferred, since a
conversion factor of 0.1 means that the transferred
value will be multiplied by 0
.1. A value of 100 will,
therefore, be understood as 10.0.
Index Factor
74 3.6
2 100.0
1 10.0
0 1.0
-1 0.1
-2 0.01
-3 0.001
-4 0.0001
■ Parameter Values
Standard Data Types
Standard data types are int16, int32, uin
t8, uint16
and uint32. They are stored as 4x registers (40001 –
4FFFF). The parameters are read using function 03
HEX
"Read Holding Registers." Par
ameters are written using
function 6
HEX
"Preset Single Register" for 1 register (16
bits), and function 10
HEX
"Preset Multiple Registers" for
2registers(32bits). Vali
d sizes to read are 1 register
(16 bits) and through 10 registers (20 characters).
Nonstandard Data Types
Nonstandard data types are text strings and are stored
as 4x registers (4000
1 – 4FFFF). The parameters are
read using function 03
HEX
"Read Holding Registers"
and written using function 10
HEX
"Preset Multiple
Registers." Va
lid sizes to read are 1 register (2
characters) through 10 registers (20 characters).
MG.10.S2.02 - VLT is a registered Danfoss trademark
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