7.3.13 Process Words (PCD)
The block of process words is divided into two blocks of
16 bits, which always occur in the defined sequence.
PCD 1
PCD 2
Control message (master
⇒
slave Control
word)
Reference value
Control message (slave
⇒
master) Status
word
Present output
frequency
7.4 How to Access Parameters
7.4.1 Parameter Handling
The PNU (Parameter Number) is translated from the
register address contained in the Modbus read or write
message. The parameter number is translated to Modbus
as (10 x parameter number) DECIMAL.
7.4.2 Storage of Data
The Coil 65 decimal determines whether data written to
the unit is stored in EEPROM and RAM (coil 65 = 1), or only
in RAM (coil 65 = 0).
7.4.3 IND
The array index is set in Holding Register 9 and used when
accessing array parameters.
7.4.4 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
truncated. If the read request for a parameter is for fewer
characters than the parameter stores, the response is
padded with spaces.
7.4.5 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
Parameters section
.
7.4.6 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." Parameters 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
characters).
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