TagDisableAlarms - Disable alarms associated with a tag

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The TagDisableAlarms function block disables all of the alarms associated with a tag.

The function block disables the alarms by sending a DisableAlarms tag command to the tag. The function block provides status information to:


The TagDisableAlarms function block has these parameters:

Parameter Type Direction Description
REQ BOOL R_EDGE Input A rising edge starts the DisableAlarms tag command.
TAGNAME STRING Input The name of the tag to send the DisableAlarms tag command to.
BUSY BOOL Output Set to TRUE while the DisableAlarms tag command is in progress.
DONE BOOL Output Set to TRUE for 1 execution after the DisableAlarms tag command has completed.
ERROR BOOL Output Set to TRUE if the DisableAlarms tag command failed.
ERRORMSG WSTRING Output If ERROR is TRUE, the reason why the DisableAlarms tag command failed.


Once the DisableAlarms tag command begins, additional requests from the input signal REQ are ignored until the tag command completes.

These timing diagrams show the relationship of the REQ, BUSY, DONE, and ERROR signals processing two requests. The first request completes with an error, the second request completes normally:

        +--------+     +-+ +------+
  REQ   |        |     | | |      |
      --+        +-----+ +-+      +------

        +------+       +------+
 BUSY   |      |       |      |
      --+      +-------+      +----------

               ++             ++
 DONE          ||             ||

ERROR          |       |
      ---------+       +-----------------

The BUSY signal is TRUE while the tag command is in progress. The DONE signal is TRUE for 1 execution after the completion of the tag command.

Example Program

The following IEC 61131-3 Program shows:

  1. A FALSE to TRUE transition of a digital data point tag used to trigger a function block.
  2. The function block disabling alarms on another tag.
  3. Example logic to check the status of the function block.
Program MAIN
        (* The function block declaration *)
        DisableFB : TagDisableAlarms;

        (* The tag used to trigger the automatic alarm disable 
           Note: Uses a relative tag reference to 'Digital Trigger Tag' 
                 located in the same folder as this program *)
        TriggerTag AT %".Digital Trigger Tag" : BOOL;

    (* Call the TagDisableAlarms function block *)
        TAGNAME:="Tag to Disable Alarms on" );

    (* The DONE output is active for one cycle when the function block completes *)
    IF DisableFB.DONE THEN

        (* Was there an error ? *)
        IF DisableFB.ERROR THEN
            (* Handle any error *)
            (* Any additional work on successful completion *)


Further Information

DisableAlarms Tag Command

To learn about the DisableAlarms tag command.

Tag Command Function Blocks

To learn about other tag command function blocks.

Elementary Data Types

To learn about the different types supported by Fernhill SCADA.

Common Elements

To learn about other IEC 61131-3 Common Elements.


For the meaning of terms used in Fernhill SCADA.