Siemens SICAM MMU 7KG9663, Device Manual, Page: 155 / 262

9 Communication
9.2 Modbus
155 SICAM MMU 7KG9663, Device Manual
E50417-H1040-C514-A3, Edition 01.2016
9.2.6.1 Data Type - Measured Value
The Measured Value data type is transferred into 2 holding registers in 32-bit floating-point format (single pre-
cision) 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
38
.
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)
<sign>
* +Inf
Exponent = 255, mantissa not equal to 0: Resulting value = NaN
0 < Exponent < 255: Resulting value = (-1)
<sign>
* 2
(<exponent> - 127)
* 1, <mantissa>
Status and Quality Information
SICAM MMU uses floating-point values with the exponent 255 (Inf, NaN) to display status information of the
measured values:
Byte 3 (MSB) Byte 2 Byte 1
S
Holding register 02xx
Byte 0 (LSB)
Exponent (8 bit)
Mantissa (23 bit)
... ...
Holding register 02xx+1
Table 9-3 Floating-point Values
Floating-point Value
(hexadecimal)
State Remark
7F800000H +Inf Overflow Measured value overflow
(> 1.2 V
rated
, > 2 I
rated
)
7F800001H NaN invalid For example, frequency not measured because mains
voltage too small
(< 15 % V
rated
)
7F800002H NaN not calculated Measured value is not calculated, for instance because
it does not exist in the selected network type.
SICAM-MMU_7KG9663_US.book Page 155 Monday, December 7, 2015 12:22 PM