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Entry type: FAQ Entry ID: 26118266, Entry date: 08/03/2007

How do you implement the "Clean Screen" function for cleaning the touch screen on Mobile Panels and OP 177B?

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With Windows-based touch panels you have the option of using the "Clean Screen" function to disable the touch surface in order to clean it. Mobile Panel 17x, Mobile Panel 277 and OP 177B do not support this standard function (see Entry ID: 14557829).

The sample program that is available in this entry for downloading contains two versions for simulating the Clean Screen function for these panels.

Please note the following restrictions when implementing the sample program:

  • The simulated Clean Screen only disables the touch surface of the panel. All other controls on the device remain active during the cleaning phase.
  • The permanent window (see also: Notes on the permanent window) can not be disabled with this function if you have configured the permanent window.

Implementing the "Clean Screen" function on OP 177B without PLC job

No. Procedure
  • In your project you add a screen entitled "Clean Screen".
  • The "Clean Screen" screen has no controls, only the lettering "Clean Screen". Press "F2" to escape.
  • There is a key in the template for this, here "F2", that is to be assigned with screen selection for Clean Screen, here "Cleanscreen".

Fig. 01

2 In "Cleanscreen", the global assignment of key "F2" is overwritten by a local assignment with "ActivatePreviousScreen".

Fig. 02

Implementing the "Clean Screen" function on OP 177B with PLC job

No. Procedure
  • In your project you add a screen entitled "Clean Screen".
  • The "Clean Screen" screen has no controls, only the lettering "Clean Screen".
  • Add a Boolean tag (in a marker area or DB in the controller) to your project.
  • Configure the "Set_bit" function with this tag as parameter on a global key in order to trigger a program with it in the controller. The program in the controller enables selection of the clean screen on the panel.

Fig. 03

2 Insert the "Job Mailbox" and "Screen Number" area pointers in your WinCC flexible project in order to implement the "Clean Screen" function. The job mailbox is needed to be able execute control jobs like "Screen Selection" on the OP 177B. The "Screen Number" user-data area displays information about the screen just selected on the OP 177B (e.g. current screen number, field number). This information is required to display the previous screen on the panel after the cleaning phase with the "Clean Screen".

Fig. 04

More information on the "Screen Number" and "Job Mailbox" area pointers are available in the communication manual for Windows-based systems in Entry ID: 1405528.

3 Description of the STEP 7 program
The STEP 7 program consists of OB1, FB100 and its instance data block DB100.
  • FB100
    If the Boolean tag created in WinCC flexible is set, the current screen number and field number from the "Screen Number" interface area (WinCC flexible area pointer) are stored in static tags. Then the parameters of the "Screen Selection" job (job number 51) are written to the job mailbox. Please note that as screen number for the job you must specify the screen number of the "Clean Screen" screen. As final parameter you enter the job number 51 in the area of the job mailbox provided so that the control job can be executed. The "Clean Screen" screen is displayed on the panel. You can set the display time of the "Clean Screen" screen with a timer. Once the timer time expires, the "Screen Selection" job is executed again with the static tags as parameters in order to activate the original screen.
  • DB100
    In DB100 are the "Job Mailbox" and "Screen Number" area pointers, the static tags for storing the screen and field numbers and the Boolean tag for activating the "Clean Screen" screen.
  • OB1
    In OB1 a check is made whether the job mailbox is free (job number = 0) and then FB100 with instance DB is called.
The STEP 7 and WinCC flexible project as download
The example includes a STEP 7 V5.4 project with a CPU 316-2DP and two OP 177Bs. It was created with STEP 7 V5.4 SP1 HF2 and WinCC flexible 2005 SP1 HF7. The example has the functionality described above.

OP177B_Cleanscreen.zip ( 4542 KB )

Open and copy the "OP177B_Cleanscreen.zip" file into a separate directory. Unpack the STEP 7 project with integrated WinCC flexible project with all the associated subdirectories. You can then use the SIMATIC Manager and WinCC flexible to open and process the extracted project.

Notes on the permanent window:
If you use a permanent window in which there are active elements (e.g. input fields, button), you can still use the clean screen. For this you must define a Boolean tag which needs no controller connection. Then this tag is assigned to the active objects in the permanent window under "Visible" and hidden with Value 1. In the clean screen, for this tag only the SetBit function has to be assigned in the "Set up" event, and the ResetBit function for the "Cleared down" event. This ensures that these objects are not operated inadvertently during cleaning.

MP170, MP177, MP277, OP177, Clean, Inoperable touch, Touch screen

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