Parameter value (PWE)
The pa-
rameter value block consists of 2 words (4 bytes), and
the value depends on the defined command (AK). If
the master prompts for a parameter value, the PWE
block does not contain a value.
If you wish the master to change a parameter value
(write), the new value is written in the PWE block and
sent to the slave.
If the 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 not a numerical value, but sev-
eral data options, e.g. parameter 001 Language where
[0] corresponds to English , and [3] corresponds to
Danish, the data value is selected by entering the value
in the PWE block. See Example - Selecting a data val-
ue.
Via serial communication it is only possible to read pa-
rameters that have data type 9 (text string). Parameter
621 - 635 Nameplate data is data type 9. For example,
in parameter 621 Unit type it is possible to read the unit
size and mains voltage range.
When a text string is transferred (read) the length of
the telegram is variable, as the texts are of different
lengths. The telegram length is defined in the tele-
gram's second byte, known as LGE.
To be able to read a text via the PWE block the pa-
rameter command (AK) must be set to 'F' Hex.
The index character is used to indicate whether it is a
read or write command.
In a read command the index must have the following
format:
Some frequency converters have parameters to which
a text may be written. To be able to write a text via the
PWE block the parameter command (AK) must be set
to 'F' Hex.
For a write command the text must have the following
format:
Data types supported by frequency converter:
Data types
Description
3 Integer 16
4 Integer 32
5 Unsigned 8
6 Unsigned 16
7 Unsigned 32
9 Text string
10 Byte string
13 Time difference
33 Reserved
35 Bit sequence
Unsigned means that there is no operational sign in
the telegram.
Example - Write a parameter value:
Parameter 202 Output frequency high limit, f
MAX
to be
changed to 100 Hz. The value must be recalled after
a mains failure, so it is written in EEPROM.
PKE = E0CA Hex - Write for parameter 202
Output frequency high limit, f
MAX
IND = 0000 Hex
PWE
HIGH
= 0000 Hex
PWE
LOW
= 03E8 Hex - Data value 1000, cor-
responding to 100 Hz, see conversion.
The response from the slave to the master will be:
Example - Selection of a data value:
You wish to select kg/hour [20] in parameter 416 Proc-
ess units. The value must be recalled after a mains
failure, so it is written in EEPROM.
PKE = E19F Hex - Write for parameter 416
Process units
IND = 0000 Hex
PWE
HIGH
= 0000 Hex
PWE
LOW
= 0014 Hex - Select data option kg/
hour [20]
VLT
®
5000 Design Guide
MG.52.B2.02 - VLT
®
is a registered Danfoss trademark 87
Serial communication
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