53
Programming Restrictions
Section 2-4
If Timer Instructions are being used, always use the Always ON Flag (P_On)
for the EN input condition and include the instruction’s input condition within
the function block definition.
• If the same instance containing a timer is used in multiple locations at the
same time, the timer will be duplicated.
2-4-2 ST Programming Restrictions
Restrictions when
Using ST Language in
Function Blocks
• 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
• Function block calling statements
• Arithmetic operators
• Logical operators
• Comparison operators
• Numerical functions
• Arithmetic functions
• Standard text string functions
• Numeric text string functions
• OMRON expansion functions
• Comments
• The TIMER and COUNTER data types cannot be used.
For further details, refer to SECTION 5 Structured Text (ST) Language Speci-
fications in Part 2: Structured Text (ST).
FB1
EN ENO
U P
LD EN
TIM tim UP
0.00
The timer’s Completion Flag (UP)
will not be turned OFF even though
input condition 0.00 goes OFF.
Body
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
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