Example including execution check

At a Glance

The following example illustrates the WRITE_VAR function with a management parameter check.

Programming the function

Programming in ST:

IF NOT %M20 AND %I0.1.2 THEN

   %MW200:4:= 0;

   INC %MW1700

   %MW202:= 50;

  WRITE_VAR(ADDR(’0.3.1.7’),’%MW’,20,1,%MW1700:1,%MW200:4);

   SET %M20;

END_IF;

the input bit %I0.1.2 controls the function,
the internet bit %M20 is used to test the activity of the function,
%MW200:4:= 0; sets the management table to 0,
INC %MW1700; increments the word %MW1700,
MW202:= 50; initializes the timeout value to 5 seconds.

NOTE: WRITE_VAR(ADDM(‘0.3.1.7’),’%MW’,20,1,%MW1700:4,%MW200:4); syntax must be used for Modicon M340 PLCs as ADDR function cannot be used by a Modicon M340 PLC.

Programming the exchange check

Programming in ST:

IF %M20 AND NOT %M200.0 THEN

   INC %MW204;

   IF %MW201 = 0 THEN

      INC %MW205;

   ELSE

      SET %Q0.2.2;

      INC %MW206;

      %MW207 := %MW201;

   END_IF;

END_IF;

%MW204 counts the number of exchanges,
%MW205 counts the number of correct exchanges,
%MW206 counts the number of exchanges generating errors,
%MW207 stores the error message,
%Q0.2.2 indicates an exchange failure.