Applies To:
  • CitectSCADA 3.00
Summary:
Question: Does ReRead() have any effect on the data returned from the TagRead() function? 

Solution:
The ReRead() function will read any I/O Device data associated with a task and referenced via the normal use of a tag. ReRead() has no effect on data returned from the TagRead() function. Each time you call TagRead() a new read will be generated to the I/O server for the requested variable. This is very similar to doing a ReRead() for that variable every time you call TagRead(). For example:

TagRead("MyTag");

is very similar to:

FUNCTION
MyFunc()
   INTEGER nValue;
   ReRead(0);
   RETURN MyTag;
END

This is why TagRead() will be slow to execute as it causes a read from the I/O Server, see also Q1456.

 
Keywords:
 

Attachments