Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 38

Precautions
• Before placing a tag FB on the FBD/LD editor, declare the tag FB on the "Tag FB Setting" window.
• Do not use a process control function block in program files with the process control extension disabled. Doing so causes
an error in programs.
• In a program and the function blocks/functions used in the program which are enabled the process control extension, the
timer (T), retentive timer (ST), and timer FB (TIMER__M) do not correctly operate. Create a program using the long timer
(LT), long retentive timer (LST), pulse timer (TP(_E)), on delay timer (TON(_E)), or off delay timer (TOF(_E)).
• In a program and the function blocks/functions used in the program which are enabled the process control extension, set an
execution cycle so that the count input signal turns on and off in a cycle longer than the execution cycle. If the count input
signal of the counter (C), long counter (LC), or counter FB turns on and off in a cycle shorter than the execution cycle, the
rising edge of the count input signal cannot be detected and an intended value may not be obtained.
• In a program and the function blocks/functions used in the program which are enabled the process control extension, a
value obtained when a program is executed is stored in the special relay (SM).
2 PROCEDURE BEFORE USING PROCESS CONTROL FUNCTION BLOCK
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2.4 Editing an FBD/LD Program for Process Control