Measured Values And Statistic Values - Siemens SIPROTEC PROFINET IO Manual

2 PROFINET IO in SIPROTEC
2.3 Data-Type Definitions for IO Data Exchange
2.3.4

Measured Values and Statistic Values

Number of byte values:
Range of values:
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:
1 bit
S
...
Byte 3 (MSB)
Figure 2-8
In DIGSI, these values have the following data type:
• Measured values: data type measured value MV
• Statistic values:
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)
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.
Table 2-2
Floating-point number
(hexadecimal)
0x7F800000
0x7F800001
0x7F800002
0xFF800000
24
4 (32 bits)
38
±1.7 * 10
8 bits
Exponent
Byte 2
Data Type: Measured Value/Statistic Value
data type value indication VI
Quality Information
Overflow
Invalid
Not calculated
Falling below
SIPROTEC 4, Communication Module PROFINET IO, Communication Profile
23 bits
Mantissa
Byte 1 Byte 0 (LSB)
<sign> (<exponent> - 127)
* 2 * 1,<mantissa>
Status
Overflow of the measured value
Measured value invalid or not computable,
for example frequency or cos φ when
voltage or current is too low.
The internal data image was not updated
after a restart.
Falling below the measured value
...
Remark
C53000-L1840-C360-1, Edition 08.2012