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Entry type: FAQ, Entry ID: 19439876, Entry date: 03/16/2007

How can I acknowledge alarms in WinCC flexible via the PLC?

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Proceed as follows to acknowledge error messages via the controller.

In WinCC flexible there is no "Alarm Ack. PLC" pointer as in ProTool.

No. Procedure
1 STEP 7 configuration:
First define a data area in your STEP 7 configuration (in this example DB10.DBW0).
Half of this data area contains the bits for the error message and the other half bits for the acknowledge area.
For example, to create a data area for 32 error messages you create an array of the "WORD" type with a length of 4 words.

Word 0 and Word 1  =>  32 message bits
Word 2 and Wort 3  =>  32 PLC acknowledge bits
Array length of 4 words. 

Fig. 01

For example, to create a data area for 128 error messages you create an array of the "WORD" type with a length of 16 words.

2 Definition of the individual error message and acknowledge bits:
Refer also to Entry ID 24638486. There you will find a Microsoft Excel table which you can use to easily display the error message and acknowledge assignment.
3 Configuring WinCC flexible:
  • In WinCC flexible, under "Communication > Tags", you insert the tag that you previously defined for the error message area - in this example DB10.DBW0.
  • Open the bit messages via "Messages > Picture message".
    Right-click the header line and, if not yet selected, add the functions "Write acknowledge tag" and "Write acknowledge bit".

Fig. 02
  • In the "Trigger Tag" field you enter the tag for the error message area - in this example DB10.DBW0.
  • Via the mass generation procedure (mark the "Trigger Tag" field, select the the bottom left corner and then move the mouse down) you fill in the subsequent fields until you have created all the 32 messages for this example.
  • Once you have configured the 32 messages you enter the same tag in the "Write acknowledge tag" field as you used in the "Trigger Tag" field. Fill in the subsequent fields also using the mass generation procedure.

Fig. 03

Make sure that the "Bit numbers" and "Write acknowledge tag bit" are assigned correctly to the separate messages.
You can use the Excel list mentioned in Point 2 as a check.

4 Testing the error message and acknowledgment:
This example includes a tag list "Vat_Bit" in the STEP 7 project. You can use this tag list to simulate the error messages 1 to 8 and acknowledge the messages.
5 Tip on the mass generation procedure:
Using the mass generation procedure you can simply and efficiently assign values to large areas.
  • Mark the "Trigger Tag" field, for example. Go with the mouse pointer over the bottom left corner until the mouse pointer changes its appearance (becomes a "cross").

Fig. 04
  • Press and hold the left mouse button and drag the "area" down until all the necessary fields are marked.

Fig. 05
  • Release the left mouse button.
    The data of the first entry is entered in the fields marked.

Runnability and test environment:
The example can be used on all the CPU types of SIMATIC S7-300, S7-400 and WinAC.
The following table lists the components that have been used to create this entry and verify the functions described.

Components Product and version designation
PC operating system Microsoft Windows XP SP2
Standard tools STEP 7 V5.3 SP3
Engineering tools -
HMI software WinCC flexible 2005 SP1 HF6
HMI devices MP370 Touch
Controllers S7 CPU 315-2DP
Table 1: Creation environment of the download attached

The attached download contains a STEP 7 project with the functions described above.

Attachment 1: PLC_ACK ( 2894 KB )

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