CASE statement in ST

Syntax
`CASE ... OF` `...` `ELSE ...` `END_CASE`

Meaning

Use the CASE statement to specify that a group of statements is to be executed, if the evaluated value of the selector (entered after CASE) corresponds to a label which is entered for this group of statements. If the value of the selector does not correspond to any of the labels, then either no statement is to be executed, or the statement group following the ELSE keyword is to be executed,

Restriction

You are only allowed to enter such →expressions for the selector that can be evaluated to be of the →generic data type ANY_INT.

A label may be one or more integer →literals/→variables, enumerated values or subranges and must be evaluated as →constant value during the runtime. The data type of the labels must be implicitly convertible into the data type of the selector.

Detailed explanation about CASE

Part of CASE statement

Explanation

CASE selector OF

  1: statements-A;

  2, 3: statements-B;

  4..6, 7: statements-C;

...

If the value of the selector corresponds to label 1 (hence: in case of value = 1), the execution continues with the statement block statements-A. After processing the last statement, the execution continues after END_CASE.
In case of value = 2 or 3, the execution continues with the statement block statements-B. After processing the last statement, the execution continues after END_CASE.
In case of value = 4, 5, 6 or 7, the execution continues with the statement block statements-C. After processing the last statement, the execution continues after END_CASE.

Each statement block may contain as many statements as you like. You may insert as many labels and statement blocks as you like. If you enter the same value for labels, the statement block first entered is selected for execution because Neuron Power Engineer compares from top to bottom.

ELSE

statements-n;

The statement block behind ELSE is only processed, if none of the labels matches the value of the selector. The statement block may contain as many statements as you like. After processing the last statement, the execution continues after END_CASE.

You may skip the ELSE-part.

END_CASE;

This concludes the CASE-statement.

Example

Example
`FUNCTION_BLOCK ExampleIfAndCaseDocumentation` `VAR` `up : BOOL;` `count : INT;` `notify : STRING[1000];` `END_VAR` `VAR CONSTANT` `neg100 : int := -100;` `neg1 : int := -1;` `END_VAR` `IF up THEN /* If 'up' = 'TRUE', counter counts up. /` `count := count + 1;` `ELSE` `count := count - 1;` `END_IF;` `CASE count OF / If 'count' is in the respective range of values, 'notify' displays the appropriate text. /` `0 : notify := 'Counter is 0.';` `1..100 : notify := 'Counter is in the range between 1 and 100.'; / This label defines a subrange with integer values. /` `neg100..neg1 : notify := 'Counter is in the range between -100 and -1.'; / This label defines a subrange with constant variables. */` `ELSE` `notify := 'Counter is more than 100 or less than -100.';` `END_CASE;` `END_FUNCTION_BLOCK`

FUNCTION_BLOCK ExampleIfAndCaseDocumentation

VAR

      up : BOOL;

      count : INT;

      notify : STRING[1000];

  END_VAR

  VAR CONSTANT

      neg100 : int := -100;

      neg1 : int := -1;

  END_VAR

  IF up THEN          /* If 'up' = 'TRUE', counter counts up. */

      count := count + 1;

  ELSE

      count := count - 1;

  END_IF;

  CASE count OF      /* If 'count' is in the respective range of values, 'notify' displays the appropriate text. */

      0            : notify := 'Counter is 0.';

      1..100       : notify := 'Counter is in the range between 1 and 100.';    /* This label defines a subrange with integer values. */

      neg100..neg1 : notify := 'Counter is in the range between -100 and -1.';  /* This label defines a subrange with constant variables. */

  ELSE

      notify := 'Counter is more than 100 or less than -100.';

  END_CASE;

END_FUNCTION_BLOCK