Parameter Value (Pwe); Data Types Supported By The Adjustable Frequency Drive; Conversion; Process Words (Pcd) - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

RS-485 Installation and Set...

7.4.10 Parameter Value (PWE)

The parameter value block consists of two words (4 bytes),
and the value depends on the defined command (AK). The
master prompts for a parameter value when the PWE block
contains no value. To change a parameter value (write),
write the new value in the PWE block and send from the
master to the follower.
When a follower responds to a parameter request (read
command), the present parameter value in the PWE block
is transferred and returned to the master. If a parameter
contains several data options, e.g., 0-01 Language, select
the data value by entering the value in the PWE block.
Serial communication is only capable of reading
parameters containing data type 9 (text string).
7 7
15-40 FC Type to 15-53 Power Card Serial Number contain
data type 9.
For example, read the unit size and AC line voltage range
in 15-40 FC Type. When a text string is transferred (read),
the length of the message is variable, and the texts are of
different lengths. The message length is defined in the
second byte of the message (LGE). When using text
transfer, the index character indicates whether it is a read
or a write command.
To read a text via the PWE block, set the parameter
command (AK) to 'F' Hex. The index character high-byte
must be "4".
7.4.11 Data Types Supported by the
Adjustable Frequency Drive
Unsigned means that there is no operational sign in the
message.
Data types
3
4
5
6
7
9
Table 7.8 Data Types
92
Design Guide
Description
Integer 16
Integer 32
Unsigned 8
Unsigned 16
Unsigned 32
Text string
Danfoss A/S © Rev. 2014-01-14 All rights reserved.

7.4.12 Conversion

The various attributes of each parameter are displayed in
the chapter Parameter Lists in the Programming Guide.
Parameter values are transferred as whole numbers only.
Conversion factors are therefore used to transfer decimals.
4-12 Motor Speed Low Limit [Hz] has a conversion factor of
0.1.
To preset the minimum frequency to 10 Hz, transfer the
value 100. A conversion factor of 0.1 means that the value
transferred is multiplied by 0.1. The value 100 is thus
perceived as 10.0.
Conversion index
74
2
1
0
-1
-2
-3
-4
-5
Table 7.9 Conversion

7.4.13 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
Control message (master⇒ follower Control
word)
Control message (follower⇒ master) Status
word
Table 7.10 Process Words (PCD)

7.5 Examples

7.5.1 Writing a Parameter Value
Change 4-14 Motor Speed High Limit [Hz] to 100 Hz.
Write the data in EEPROM.
PKE=E19E Hex - Write single word in 4-14 Motor Speed High
Limit [Hz]:
IND=0000 Hex
PWEHIGH=0000 Hex
PWELOW=03E8 Hex
Conversion factor
0.1
100
10
1
0.1
0.01
0.001
0.0001
0.00001
PCD 2
Reference value
Present output
frequency
MG18C522