Siemens Sentron 7KN POWERCENTER 1000 Manual page 66
Circuit protection devices with communication and measuring function
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Functions
6.4 Modbus TCP connection
Individual units of information are identified by register addresses. A register is 16 bits in size.
If a unit of information is larger than 16 bits, it will require the corresponding number of
registers.
Example of the representation by means of a 32-Bit floating point number FP32 according to
IEEE 754
Example of the representation of a 67-Bit floating point number FP67 according to IEEE 754
Example of the representation of a time stamp based on a FP64 number
Invalid values
Due to temporary events, e.g. interruption of supply voltage or communication, it is
necessary to check the contents of registers for validity. Invalid measured values are marked
as Not a Number (NaN according to IEEE-754). The connection status of a terminal device is
stated via the "Device status" data point of the respective device. This is used to conclude
whether the communication of the terminal device can be established and thus current
values can be read. If validity is important for an application, the measured values must be
checked for not equal to "NaN" and the device status equals "3 = connected" before
processing. This applies to all 1 - 24 terminal devices.
Intervals
It is recommended to query each device no more than 1x per second. The terminal devices
must be addressed individually and should be processed sequentially. The measured values
are updated at least every 2 s (see Measured value transmission frequency (Page 54)).
If possible, several registers should always be polled in blocks instead of sending one protocol
per register.
64
Circuit protection devices with communication and metering function
System Manual, 06/2021, L1V30827018B-01
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