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Entry type: FAQ Entry ID: 107146628, Entry date: 06/08/2015
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What should you watch out for with communication by text message (SMS) between a LOGO! CMR and a LOGO! 8 with values of the data type BYTE, WORD or DWORD?

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With LOGO! CMR it is possible to write values to the LOGO! 8 via SMS text messages and to read out values from LOGO! 8. This entry explains what you should watch out for with communications between the LOGO! CMR and the LOGO! 8.

Description
With the LOGO! CMR values can be written to the variable memory (VM) of a LOGO! 8 or read from the variable memory (VM) of a LOGO! 8 via SMS text messages.

In this entry the term "LOGO! CMR" refers to both the LOGO! CMR2020 and the LOGO! CMR2040.

In the web interface (WBM), with which the LOGO! CMR is configured, you can specify a threshold value for a value from the LOGO! 8, for example. If the threshold value is then exceeded or not reached by the value from the LOGO! 8, it can be defined that an SMS text be sent to one or more recipients (trigger event). 


If for communication from the LOGO! CMR to the LOGO! 8 by SMS text a value of the data type BYTE, WORD or DWORD is used, you must pay attention to the interpretation in the following applications.

  • When defining threshold values for values from the LOGO! 8 in the web interface (WBM) of the LOGO! CMR.
  • When displaying values from the LOGO! 8 in the web interface (WBM) of the LOGO! CMR.
  • When writing values to the LOGO! 8 or when reading values from the LOGO! 8 via SMS text with the LOGO! CMR.

The LOGO! CMR and the LOGO! 8 interpret all values of the data type BYTE, WORD and DWORD as type "with sign" which means signed. Note this in particular when configuring threshold values with the LOGO! CMR, in other words always specify the relevant values signed.

Values written via SMS text to the LOGO! 8 or read from the LOGO! 8 are interpreted by the LOGO! CMR likewise always as values "with sign".

Range of values for writing/ reading values of the LOGO! 8 with the LOGO! CMR
 

Data type

Length in the

variables memory

Range of values

BIT 1 bit 0, 1
BYTE 1 byte

-128...127

WORD 2 byte -32,768...32,767
DWORD 4 byte

−2,147,483,648...2,147,483,647

The data type BIT id from the firmware version V2.0 of the LOGO! CMR available. The firmware update can be found at the Entry ID 109742966.

Further Information
about communication by a LOGO! CMR with a LOGO! 8 is available in the manual in Entry ID 109745580.

  • Information about writing values to/reading values from the LOGO! 8 with the LOGO! CMR in the chapter "SMS commands".
  • How to monitor the value of a LOGO! 8 with the LOGO! CMR is described in the chapter "Monitoring".
  • What to watch out for when writing/reading values to/from the LOGO! 8 with the LOGO! CMR is described in the chapter "Operation".

Further information about working with unsigned and signed numbers is available in Wikipedia, for example, by entering the keyword "two's complement".

Creation Environment
The screens in this FAQ response were created with the web interface (WBM) of the LOGO! CMR (FW V2.0).

Additional Keywords
Alarm generation, Remote access, Remote diagnostics, Plant state, Data communication, Control command, Communication system

Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit
https://www.siemens.com/cybersecurity#Ouraspiration.
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