Dummy Step; Coil Hold Step - Mitsubishi Electric MELSEC-Q Series Programming Manual

Operation of the initial steps with step attributes
The operation of the initial steps with step attributes is the same as that of the other steps. Refer to Page 46 Coil HOLD step
to Page 51 Reset step.

Dummy step

A dummy step is a waiting step, etc., which contains no operation output program.
• The transition condition following the corresponding step is always checked during execution of a dummy step, and
execution proceeds to the next step when the transition condition is satisfied.
• The dummy step changes to a step (without step attribute, indication: ) when an operation output program is created.

Coil HOLD step

A coil HOLD step is a step where the coil output status is maintained in the transition to the next step. (The coil output is
switched ON by the OUT instruction when the transition condition is satisfied.)
Coil switched ON by the OUT instruction when the transition condition is satisfied
During normal SFC program operation, the coil ON status (switched ON by OUT instruction when transition condition is
satisfied) is automatically switched OFF before proceeding to the next step. By designating an operation output step as a "coil
HOLD step", the coil ON status will remain in effect when proceeding to the next step.
At a designated coil HOLD step, "Y10" (switched ON
by OUT instruction) will remain ON even when the
transition condition is satisfied.
Ladder processing occurred after a transition to the next step
No ladder processing occurs following a transition to the next step.
Timing at coil is turned off when coil at coil HOLD step has been turned on to next step
When a coil ON status (at coil HOLD step) has been maintained to the next step, the coil will be switched OFF at any of the
following times:
• When the end step of the corresponding block is executed. (Except when SM327 is ON)
• When an SFC control instruction (rBLm) designates a forced END at the block in question.
• When an SFC control instruction (rBLm\Sn, rSn) designates a reset at the block in question.
• When a reset occurs at the device designated as the SFC information register's block START/END device.
• When a reset step for resetting the step in question becomes active.
• When the SFC START/STOP command (SM321) is switched OFF.
• When the coil in question is reset by the program.
• When the STOP instruction is executed with the stop-time output mode OFF.
• When S999 is designated at the reset step in the corresponding block.
4 SFC PROGRAM CONFIGURATION
46
4.2 Steps
At steps not designated as coil HOLD steps, "Y10"
(switched ON by OUT instruction) is automatically
switched OFF when the transition condition is satisfied.