TagResetStatistics Function Block

Help Contents

Introduction

The TagResetStatistics Function Block resets the statistics counters of a Channel Tag.

The function block resets statistics counters by sending a ResetStatistics Tag Command to the tag. The function block provides status information to:

Functions and Function Blocks

The TagResetStatistics Function Block is intended for use in a Program Tag that runs on the Fernhill SCADA Server. A Program Tag uses a continuous execution model, where the program code runs at a fixed interval. A program uses the function block to sample the state of the tag command as it executes.

If you want to reset the statistics of a tag from an Operator Action, use the TagResetStatistics Function.

Syntax

The TagResetStatistics Function Block has this syntax:

TagResetStatistics(
        REQ:=Expression,
        TAGNAME:=Expression,
        BUSY=>Variable-Reference,
        DONE=>Variable-Reference,
        ERROR=>Variable-Reference,
        ERRORMSG=>Variable-Reference );

Note: All parameters are optional.

Parameters

The TagResetStatistics Function Block has these parameters:

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

Remarks

Once the ResetStatistics 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. A function block resetting the statistics counters of another tag.
  3. Example logic to check the status of the function block.
Program MAIN
    VAR 
        (* The function block declaration *)
        ResetFB : TagResetStatistics;

        (* The tag used to trigger statistics reset
           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 TagResetStatistics function block *)
    ResetFB( 
        REQ:=TriggerTag,
        TAGNAME:="Tag to reset statistics" );

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

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

END_PROGRAM

Further Information

ResetStatistics Tag Command

To learn about the ResetStatistics Tag Command.

Tag Command Function Blocks

To learn about other tag command function blocks.

IEC 61131-3 Expressions

To learn about the different types of expression to use as function parameters.

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.