×
Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 12267138, Entry date: 10/20/2010
(0)
Rate

Why are spaces displayed at the beginning of the process-associated value (text) and characters truncated at the end?

  • Entry
  • Associated product(s)

Description
An 8-bit text tag is linked to an I/O field in WinCC. The associated value in the AS is to be displayed as such in the Alarm Logging Control and sent with SFB 35. This user-configured text tag is written to the AS as an S7 string. However, this data type has a header of 2 bytes which is not displayed.

Message-associated values are not of the "S7 string" type, but arrays of the CHAR type. The AS then sends the data as additional value as of a specified start address. If this address is put at the start of the above-mentioned text tag, the text including the header is displayed in the Alarm Logging Control. In order to avoid this, you must increase the start address by 2 bytes.

Example
In the Tag Management, the string variable "varOtto" is configured with the address DB10.DBB16. If you write this variable with the text "anna", you have the following text as of DB10.DBB16:
"0A 04 a n n a". If you assign the parameter SD_n := P#DB10.DBX16.0 CHAR 4, when a message arrives, it transfers the header and two following characters, in this case therefore:
"0A 04 a n"
. In order to display the associated value correctly, you must set the following parameter: SD_n := P#DB10.DBX18.0 CHAR 4.

Fig. 1: Variable "varOtto" in the WinCC Tag Management, in the Step 7 data block and in the variable table ( 277 KB )  

Keyword:
Message configuration, Message-associated value

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.
Rate entry
no rating
Requests and feedback
What do you want to do?
Note: The feedback always relates to the current entry / product. Your message will be forwarded to our technical editors working in the Online Support. In a few days, you will receive a response if your feedback requires one. If we have no further questions, you will not hear from us.