Danfoss VLT PROFIBUS DP MCA 101 Programming Manual page 32

Parameter Access
5.2.17 Attribute Description (20 H)
The attribute description allows access to the parameter
description. It is possible to read out 1 single description
element, or all elements for 1 parameter in 1 telegram.
Table 5.10 provides an overview of the existing parameter
description, which exists for each parameter in the
frequency converter.
Subindex Description
1 Identifier ID
5 5
2 Number of array
elements or length or
string
3 Standardization factor
4 Variable attribute
5 Reserved
6 Name
7 Lower limit
8 Upper limit
9 Reserved
10 ID extension
11 PCD reference parameter
12 PCD normalization
0 Complete description
Table 5.10 Parameter Description Elements (all Elements are
Read-only)
Table 5.11 explains each description element.
Identifier ID
Bit Description
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 Standardization factor and variable attribute not
relevant.
0–7 Data type.
Table 5.11 Extra Characteristics of a Parameter
Number of array elements
•
Contains the number of array elements, if the
parameter is an array.
•
Contains the string length, if the parameter value
is a string.
•
Contains a 0 if the parameter is neither.
30
®
VLT PROFIBUS DP MCA 101
Data type
V2
U16
Float
Octet string 2
Octet string 4
Visible string 16
Octet string 4
Octet string 4
Octet string 2
V2
U16
V2
Octet string 46
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Standardization factor
Conversion factor for scaling a given parameter value to
standard SI units.
For example, if the given value is in mV, the standardi-
zation factor is 1000, which converts the given value to V.
The standardization 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 A, V).
The second byte is the conversion index, which is a scaling
factor for the parameter. All parameters accessible by
PROFIBUS are organized and transmitted as real numbers.
The conversion index defines a factor for conversion of 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 V.
Name
Contains the parameter name, limited to 16 characters, for
example language for parameter 0-01 Language. This text is
available in the language selected in
parameter 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 maximum 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.
Therefore the process data must deliver a reference to
parameter X.
Field PCD normalization
The field PCD normalization must express the value that
shows the 100%. Thus, the normalization delivered back
must be the set bit 15 and a value of 0xe (14, 2
=0x4000), and the result must be 0x800e.
Complete description
Returns the complete parameter description with the fields
1–12 in order. Length=46 byte.
5.2.18 Attribute Text (30 H)
For some frequency converter parameters, a descriptive
text is available, which can be read using this attribute. A
bit set in the identifier (ID) parameter description element
indicates the availability of a text description for a
parameter. The description element can be read out by the
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