Short summary

Functionality

The mathematical function exponentation is called: The block returns the result of IN1IN2 (the value connected to IN1 is exponentiated by the value connected to IN2).

Observe as well:

• For ANY_REAL values:

  No check of invalid connections

  For some blocks, invalid connections are not checked by logi.CAD 3. Therefore, enter code in your application to detect invalid connections (e.g. IF-statements in the ST-code). See "Examples for invalid Connections".

  See "IEC-blocks for the application" for information what the consequences of an invalid connection might be.

  
  You might want to use the IS_VALID block in your application to check the validity of ANY_REAL values.

  Restriction

  For the platform "vxWorks x86", the EXPT block does not return "Not-a-Number" (NaN) in case of an invalid connection of the EXPT block with ANY_REAL values. See also "EXPT block returns a wrong value under certain target system in case of an invalid connection".

• For ANY_INT values (see under "Example for usage within ST-editor" ):

    ANY_INT is...

  USINT, UINT, UDINT, ULINT, SINT, INT, DINT or LINT(corresponds to →generic data type ANY_INT)

  • If the return value exceeds the upper limit of the data type, the block returns the upper limit of the data type. In this case, the output ENO is set to value FALSE.
    

  • If the return value is below the lower limit of the data type, the block returns the lower limit of the data type. In this case, the output ENO is set to value FALSE as well.

Inputs, return value

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

• "Blocks for safe logic" whether this block is supported for developing safety-relevant applications.

• "Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic .

Internal error diagnostic for block

The block checks the return value. The output ENO of the block is set to value FALSE (or an equivalent) in the following cases:

• The return value exceeds the upper limit of the data type. (Moreover for this case, the blocks returns the upper limit of the data type.)

• The return value is below the lower limit of the data type. (Moreover for this case, the blocks returns the lower limit of the data type.)

Example for usage within ST-editor

The calculated values are evaluated by using the Assert block .

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.

Examples for invalid connections

Invalid connections might occur in the following cases during a calculation using EXPT.

• due to →overflows or →underflows

  Examples for invalid connections

  FUNCTION_BLOCK ExampleExptInvalid1

  VAR

  resultSint1, resultSint2 : SINT;

  CheckENO1, CheckENO2 : BOOL;

  END_VAR

   

  resultSint1 := EXPT(IN1 := SINT#10, IN2 := SINT#3, ENO=>CheckENO1); (* The upper limit for SINT is '127'. '10**3' causes an overflow as '10**3' would evaluate to '1000'. *)

  Assert(resultSint1 = 127);

  Assert(CheckENO1 = FALSE);

   

  resultSint2 := EXPT(IN1 := SINT#-10, IN2 := SINT#3, ENO=>CheckENO2); (* The lower limit for SINT is '-128'. '-10**3' causes a negative overflow as '-10**3' would evaluate to '-1000'. *)

  Assert(resultSint2 = -128);

  Assert(CheckENO2 = FALSE);

   

  END_FUNCTION_BLOCK

• if IN1 < 0 and IN2 is not an →integer
  

  Example for invalid connections

  FUNCTION_BLOCK ExampleExptInvalid2

  VAR

  resultRealInvalid : REAL;

  END_VAR

   

  resultRealInvalid:= EXPT(IN1 := REAL#-25.0, IN2 := REAL#0.5);

  (* For the built-in PLC, 'resultRealInvalid' evaluates to 'NaN' in the 'Values of Variables* view. *)

  (* But this is not the case for vxWorks x86. *)

  ASSERT(NOT IS_VALID(resultRealInvalid));

   

  END_FUNCTION_BLOCK

See also " EXPT block returns a wrong value under certain target system in case of an invalid connection ".