Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 24)

24 Publication 1756-PM007D-EN-P - November 2012
Chapter 1 Program Structured Text
Example 3: IF…THEN…ELSIF
The [:=] tells the controller to clear Sugar.Inlet whenever the controller:
• enters the Run mode.
• leaves the step of an SFC if you configure the SFC for Automatic reset.
(This applies only if you embed the assignment in the action of the step
or use the action to call a structured text routine via a JSR instruction.)
Example 4: IF…THEN…ELSIF…ELSE
If you want this Enter this structured text
If sugar low limit switch = low (on) and sugar high limit
switch = not high (on) then IF Sugar.Low & Sugar.High THEN
inlet valve = open (on) Sugar.Inlet [:=] 1;
Until sugar high limit switch = high (off) ELSIF NOT(Sugar.High) THEN
Sugar.Inlet := 0;
END_IF;
If you want this Enter this structured text
If tank temperature > 100 IF tank.temp > 200 THEN
then pump = slow pump.fast :=1; pump.slow :=0; pump.off :=0;
If tank temperature > 200 ELSIF tank.temp > 100 THEN
then pump = fast pump.fast :=0; pump.slow :=1; pump.off :=0;
otherwise pump = off ELSE
pump.fast :=0; pump.slow :=0; pump.off :=1;
END_IF;