Danfoss VLT PROFIBUS DP MCA 101, Руководство по программированию

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5.2.17 Attribute Description (20H)
The attribute description permits access to the parameter
description. It is possible to read out one single description
element, or all elements for one parameter in one
telegram.
Table 5.10 provides an overview of the existing
parameter description, which exists for each parameter in
the frequency converter.
Sub-index Meaning Data type
1 Identifier ID V2
2 Number of array elements or
length or string
U16
3 Standardisation factor float
4 Variable attribute Octet string 2
5 Reserved Octet string 4
6 Name Visible string 16
7 Lower limit Octet string 4
8 Upper limit Octet string 4
9 Reserved Octet string 2
10 ID extension V2
11 PCD reference parameter U16
12 PCD normalisation V2
0 Complete description Octet string 46
Table 5.10 Parameter Description Elements (all Elements are
Read-only)
Table 5.11 explains each description element.
Identifier ID
Bit Meaning
15 Reserved
14 Array
13 Parameter value can be reset only.
12 Parameter has been changed from factory setting.
11 Reserved
10 Additional text array available
9 Parameter is read-only.
8 Standardisation factor and variable attribute not relevant.
0-7 Data type
Table 5.11 Additional Characteristics of a Parameter
Number of array elements
Contains the number of array elements, if the parameter is
an array; the string length, if the parameter value is a
string; or 0 if the parameter is neither.
Standardisation factor
Conversion factor for scaling a given parameter value to
standard SI units.
For example, if the given value is in mV, the standardi-
sation factor is 1000, which converts the given value to V.
The standardisation factor is in float format.
Variable attribute
Consists of 2 bytes. The first byte contains the variable
index, which defines the physical unit of the parameter (for
example Ampere, Volt).
The second byte is the conversion index, which is a scaling
factor for the parameter.All parameters accessible by
PROFIBUS are organised and transmitted as real numbers.
The conversion index defines a factor for conversion the
actual value to a standard physical unit. A conversion
index of -1 means, that the actual value must be divided
by 10 to become a standard physical unit for example,
Volt.
Name
Contains the parameter name, limited to 16 characters, for
example, LANGUAGE for
0-01 Language . This text is
available in the language selected in 0-01 Language .
Lower limit
Contains the minimum value of the parameter. Format is
32 bit signed.
Upper limit
Contains the maximum value of the parameter. Format is
32 bit signed.
ID extension
Not supported.
PCD reference parameter
Process data may be scaled by a parameter, for example,
the max reference of 0x4000 (in %) depends on the setting
of parameter X.
To enable the master to calculate the real value of the
process data, it has to know the value of parameter X, and
therefore the process data must deliver a reference to
parameter X.
Field PCD normalisation
The field PCD normalization must express, in any case, the
value that represents the 100%, that is, the normalization
delivered back must be the set bit 15 and a value of 0xe
(14, 2
14
=0x4000), and the result must be 0x800e.
Complete description
Returns the complete parameter description with the fields
1 to 12 in order. Length=46 byte.
5.2.18 Attribute Text (30H)
For some frequency converter parameters a descriptive
text is available, which can be read using this attribute.
The availability of a text description for a parameter is
indicated by a bit set in the identifier (ID) parameter
description element, which can be read out by the
description attribute (20H) sub-index=1. If bit 10 is set, a
descriptive text exists for each value of the parameter.
As an example,
0-01 Language has settings from 0 to 5. For
each of these values a specific text exists: 0=English,
2=Deutsch, and so on.
5.2.19 Format
Specifies the format type for each parameter (word, byte,
and so on), see
Table 5.12 .
Parameter Access Programming Guide
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