script

please help me to read this script.
also suggest me the link where i can learn script


IF lifting_mov3_p = true
THEN
destination_tank3 := 10;
process_number3 := 1;
END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and phosphating_only = false and process_number3 = 1
THEN destination_tank3 :=11;
process_number3 := process_number3+1;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and phosphating_only = true and process_number3 = 1
THEN destination_tank3 :=15;
process_number3 := 10;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_p = true and process_number3 = 2
THEN destination_tank3 :=12;
process_number3 := process_number3+1;
END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and process_number3 = 3
THEN destination_tank3 :=13;
process_number3 := process_number3+1;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_p = true and process_number3 = 4
THEN destination_tank3 :=13;
process_number3 := process_number3+1;
END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and process_number3 = 5
THEN destination_tank3 :=14;
process_number3 := process_number3+1;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_p = true and process_number3 = 6
THEN destination_tank3 :=14;
process_number3 := process_number3+1;
END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and process_number3 = 7
THEN destination_tank3 :=15;
process_number3 := process_number3+1;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_p = true and process_number3 = 8
THEN destination_tank3 :=11;
process_number3 := process_number3+1;
END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_n = true and process_number3 = 9
THEN destination_tank3 :=12;
process_number3 := process_number3+1;

END_IF;
IF tanknumber3 = destination_tank3 and bottom_limit3_p = true and process_number3 = 10
THEN destination_tank3 :=10;
process_number3 := 1;
END_IF;

That script seems to configure a sequence for tank filling in the PLC.

This seems pretty easy to understand... if you want to know special functions available, that will depend on your SCADA package.

This document is for AB PLC, but it will give you the basics of reading ST in any platform.

http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm007_-en-p.pdf


Bubba.