TagEnableAlarms - Enable alarms associated with a tag

Help Contents

Introduction

The TagEnableAlarms function block enables all of the alarms associated with a tag.

The function block enables the alarms by sending an EnableAlarms tag command to the tag. The function block provides status information to:

Parameters

The TagEnableAlarms function block has these parameters:

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

Remarks

Once the EnableAlarms 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 enabling alarms on another tag.
  3. Example logic to check the status of the function block.
Program MAIN
    VAR 
        (* The function block declaration *)
        EnableFB : TagEnableAlarms;

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

    (* Call the TagEnableAlarms function block *)
    EnableFB( 
        REQ:=TriggerTag,
        TAGNAME:="Tag to Enable Alarms on" );

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

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

END_PROGRAM

Further Information

EnableAlarms Tag Command

To learn about the EnableAlarms 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.

Glossary

For the meaning of terms used in Fernhill SCADA.