40
Restrictions on Function Blocks Section 2-3
• If the same instance containing a timer is used in multiple locations at the
same time, the timer will be duplicated.
ST Programming
Restrictions
• Only the following statements and operators are supported.
• Assignment statements
• Selection statements (CASE and IF statements)
• Iteration statements (FOR, WHILE, REPEAT, and EXIT statements)
• RETURN statements
• Arithmetic operators
• Logical operators
• Comparison operators
• Numerical Functions
• Arithmetic Functions
•Comments
• The TIMER and COUNTER data types cannot be used.
For further details, refer to Appendix B Structured Text (ST Language) Specifi-
cations.
Program Structure Precautions
No Branches to the Left of
the Instance
Branches are not allowed on the left side of the instance. Branches are
allowed on the right side.
Only One Instance per
Rung
A program rung cannot have more than one instance.
FB1
EN ENO
a U P
P_On
LD a
TIM tim UP
0.00
The timer’s completion flag (UP) is turned
OFF when input condition a (0.00) goes OFF.
Body
FB FB
Incorrect Correct
Instruction
Instruction
FB
FB
FB
Incorrect Incorrect
To Next Page
Loading...
