Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 129

■ Precautions
• If the continuous transition bit is turned on, execution of actions (from a transition becoming TRUE to destination step)
takes priority over the other processing. allows to shorten a takt time. In this case, however, the operations of the other
blocks and sequence program may become slower.
• The continuous transition bit is not turned off when the SFC program starts or ends.
• When a jump transition or selective convergence causes the active state to transition from multiple steps to one step, the
action of one step may be executed twice in a single scan.
(1)
• If the transition after the step becomes TRUE with the setting of "Continuous transition", a step is started or ended within
one scan. In this case, since the END processing has not been executed, the input/output refresh of coil output by using the
OUT instruction in the action is not reflected and therefore other programs cannot detect ON of the coil. In the case of
output (Y), for example, output (Y) is not output while END processing is unexecuted and other programs cannot detect
output (Y) ON. Accordingly, ON of the step relay cannot be detected, either. To reflect the I/O refresh of the OUT instruction,
create a program so that one step is executed in multiple scans.
(3)
(1)
(4)
(2)
(5)
(6)
• When creating a program that uses a jump sequence for looping, eliminate continuous transitions or prevent all transitions
in the loop from becoming TRUE during execution. If all transitions in the loop become TRUE during execution with
continuous transitions enabled, an infinite loop occurs in a single scan.
When the setting is "Continuous transition", step (1) is executed twice in a single scan.
When the transition (1) and (2) become TRUE, the following is executed in one scan.
• The action of step (3) is executed.
• As the transition (1) becomes TRUE, the action of step (3) is turned off.
• Step (3) becomes inactive and step (4) becomes active.
• As continuous transitions are enabled, the action of step (4) is executed.
• As the transition (2) becomes TRUE, the action of step (4) is turned off.
• Step (4) becomes inactive and step (5) becomes active.
• As continuous transitions are enabled, the action of step (5) is executed.
• As the transition (6) does not become TRUE, the action of step (5) is not turned off.
8 SFC PROGRAM
8.4 SFC Information Devices
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