Automating Manufacturing Systems - Process Control and ...

plc st - 19.10
• Language structures include those below,
IF-THEN-ELSIF-ELSE-END_IF;
CASE-value:-ELSE-END_CASE;
FOR-TO-BY-DO-END_FOR;
WHILE-DO-END_WHILE;
normal if-then structure
a case switching function
for-next loop
Figure 19.14
Flow Control Functions
• Special instructions include those shown below.
RETAIN()
IIN();
EXIT;
EMPTY
causes a bit to be retentive
immediate input update
will quit a FOR or WHILE loop
Figure 19.15
Special Instructions
• Consider the program below to find the average of five values in floating point
memory.