testDI function

sort

Hello all I would like to know what is the real difference between these two lines

IF DI_mySignal THEN

and  the same using IF TesetDI(DI_mySignal) THEN

Both are working but what is the real differenece?

Thank you

DenisFR

Hello,

You can write it like this too:

IF DI_mysignal=1 THEN

or

IF DI_mysignal=high THEN

But if you define badly DI_mysignal nothing happens in syntax check.

TestDI have a signaldi parameter, so it have to be defined as this.

And TestDI handles errors:

Error handling

The following recoverable errors are generated and can be handled in an error handler. The system variable ERRNO will be set to: Name Cause of error ERR_NO_ALIASIO_DEF The signal variable is a variable declared in RAPID. It has not been connected to an I/O signal defined in the I/O configuration with instruction AliasIO. ERR_NORUNUNIT There is no contact with the I/O device. ERR_SIG_NOT_VALID The I/O signal cannot be accessed. The reasons can be that the I/O device is not running or an error in the configuration (only valid for ICI field bus).

Micky

Hello,

the difference is that function "TESTDI" returns a boolean value (True or False) instead of "high" and "low".

I think there is no additional error check inside this function.

The function will probably look like this:

FUNC bool TESTDI(VAR signaldi Signal)<br>  RETURN Signal = high;<br>ERROR<br>  RAISE;<br>ENDFUNC<br>

I think if you use an "IF" statement in your code, it will be faster than calling the TESTDI function.

BR

Micky

lemster68

I found this code in an older mediapool for S4 generation controllers:

 ! Test Digital Input

 FUNC bool TestDI(VAR signaldi Signal)

  IF Signal = 1 THEN

   RETURN TRUE;

  ELSE

   RETURN FALSE;

  ENDIF

 ENDFUNC

DenisFR

I take the text from documentation.

lemster68

I see, Denis.  Makes me curious if the error is generated in the routine that calls the function or if the function has its error handler which RAISES the error.