Allen-Bradley Logix5000 Reference Manual page 683

Example 3:
If you want this
If sugar low limit switch = low (on) and sugar high limit switch =
not high (on) then
inlet valve = open (on)
Until sugar high limit switch = high (off)
Example 4:
If you want this
If tank temperature > 100
then pump = slow
If tank temperature > 200
then pump = fast
Otherwise pump = off
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
The [:=] tells the controller to clear light whenever the controller does the
following:
• 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.)
IF...THEN...ELSIF
Enter this structured text
IF Sugar.Low & Sugar.High THEN
ELSIF NOT(Sugar.High) THEN
END_IF;
The [:=] tells the controller to clear Sugar.Inlet whenever the controller does the
following:
• 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.)
IF...THEN...ELSIF...ELSE
Enter this structured text
IF tank.temp > 200 THEN
pump.fast :=1; pump.slow :=0; pump.off :=0;
ELSIF tank.temp > 100 THEN
pump.fast :=0; pump.slow :=1; pump.off :=0;
ELSE
pump.fast :=0; pump.slow :=0; pump.off :=1;
END_IF;
Structured Text Programming
Sugar.Inlet [:=] 1;
Sugar.Inlet := 0;
Appendix C
683