2 PROFINET IO in SIPROTEC
2.3 Data-Type Definitions for IO Data Exchange
24
SIPROTEC 4, Communication Module PROFINET IO, Communication Profile
C53000-L1840-C360-1, Edition 08.2012
2.3.4
Measured Values and Statistic Values
Number of byte values:
4 (32 bits)
Range of values:
±1.7 * 10
38
Measured values and statistic values are transmitted in 32 bit floating-point format. The format consists of a
sign bit (S), exponent and mantissa as shown in the following:
Figure 2-8
Data Type: Measured Value/Statistic Value
In DIGSI, these values have the following data type:
•
Measured values: data type measured value MV
•
Statistic values:
data type value indication VI
Sign Bit (S)
The sign bit (S) is set if measured values are negative.
Measured Values (Mantissa and Exponent)
The value of a measured value is obtained as follows:
0 < Exponent < 255: resulting value = (-1)
<sign>
* 2
(<exponent> - 127)
* 1,<mantissa>
Exponent = 0: resulting value = 0
Exponent = 255, mantissa not equal to 0: invalid (Not a Number, NaN)
Quality Information
"Not a Number" (NaN) floating-point numbers are used to specify the quality of measured values.
S
1 bit
8 bits
23 bits
Byte 0 (LSB)
Exponent
Mantissa
Byte 3 (MSB)
Byte 2
Byte 1
...
...
Table 2-2
Quality Information
Floating-point number
(hexadecimal)
Status
Remark
0x7F800000
Overflow
Overflow of the measured value
0x7F800001
Invalid
Measured value invalid or not computable,
for example frequency or cos
φ
when
voltage or current is too low.
0x7F800002
Not calculated
The internal data image was not updated
after a restart.
0xFF800000
Falling below
Falling below the measured value
com_profinet-io_profile_us.book Page 24 Friday, August 17, 2012 1:40 PM
