Siemens SICAM Q100 System Manual page 23

2.2.6.1 Data Type - Measured Value (Read)
The Measured Value data type is transferred into 2 holding registers in 32-bit floating-point format
(single precision) according to IEEE standard 754.
Structure of the Format
The 32-bit floating-point format consists of a sign bit (S), exponent and mantissa:
Value Range
The 32-bit floating-point format has the value range: ±(10
Value of the Measured Values
The value of a measured value is obtained as follows:
Exponent = 0: Resulting value = 0
Exponent = 255, mantissa = 0: Resulting value = (-1)
Exponent = 255, mantissa not equal to 0: Resulting value = NaN
0 < Exponent < 255: Resulting value = (-1)
Status and Quality Information
SICAM Q100 uses floating-point numbers with the exponent 255 (Inf, NaN) to display status information of the
measured values:
Table 2-4
Floating-point Number
(Hexadecimal)
7F800000H
7F800001H
7F800002H
SICAM Q100, 7KG95xx, System Manual
E50417-C1040-C522-A8, Edition 09.2020
S Exponent (8 bit)
Byte 3 (MSB)
...
Holding register 02xx
Floating-point Numbers
State
+Inf Overflow
NaN invalid
NaN not calculated
Mantissa (23 bit)
Byte 2 Byte 1
Holding register 02xx+1
-38 +38
to 10
<sign>
* +Inf
<sign> (<exponent> - 127)
* 2
Remark
Measured value overflow
(> 1.2 V , > 2 I
rated
For example, frequency not measured because mains
voltage too small
(< 15 % V )
rated
Measured value is not calculated, for instance because
it does not exist in the selected network type.
Byte 0 (LSB)
...
).
* 1, <mantissa>
)
rated
Communication
2.2 Modbus
23