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

RS485 Installation and Set-...
Only the low byte is used as an index.

7.4.10 Parameter Value (PWE)

The parameter value block consists of 2 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 slave.
When a slave 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, for example
parameter 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).
Parameter 15-40 FC Type to parameter 15-53 Power Card
Serial Number contain data type 9.
For example, read the unit size and mains voltage range in
parameter 15-40 FC Type. When a text string is transferred
(read), the length of the telegram is variable, and the texts
are of different lengths. The telegram length is defined in
nd
the 2 byte of the telegram (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
Frequency Converter
Unsigned means that there is no operational sign in the
telegram.
Data types
3
4
5
6
7
9
Table 7.8 Data Types
MG18C702
Design Guide

7.4.12 Conversion

The programming guide contains the descriptions of
attributes of each parameter. Parameter values are
transferred as whole numbers only. Conversion factors are
used to transfer decimals.
Parameter 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.
Table 7.9 Conversion

7.4.13 Process Words (PCD)

The block of process words is divided into 2 blocks of 16
bits, which always occur in the defined sequence.
Control telegram (master⇒slave control
word)
Control telegram (slave⇒master) status
word
Table 7.10 Process Words (PCD)

7.5 Examples

Description

7.5.1 Writing a Parameter Value

Integer 16
Integer 32
Change parameter 4-14 Motor Speed High Limit [Hz] to 100
Unsigned 8
Hz.
Unsigned 16
Write the data in EEPROM.
Unsigned 32
Text string
PKE = E19E hex - Write single word in
parameter 4-14 Motor Speed High Limit [Hz]:
Data value 1000, corresponding to 100 Hz, see
chapter 7.4.12 Conversion.
Danfoss A/S © 04/2016 All rights reserved.
Conversion index
74
2
1
0
-1
-2
-3
-4
-5
PCD 1
•
IND = 0000 hex.
•
PWEHIGH = 0000 hex.
•
PWELOW = 03E8 hex.
Conversion factor
3600
100
10
7
1
0.1
0.01
0.001
0.0001
0.00001
PCD 2
Reference value
Present output
frequency
85
7