Mitsubishi Q Series Programming Guide

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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
4.2.2 Initial step
The initial step represents the beginning of a block. Up to 32 initial steps per block can be
designated.
When there are more than one initial step, the coupling enabled is only a selective coupling.
Execute the initial steps in the same way as executing the steps other than the initial step.
(1) Active steps at block START
When the block that has more than one initial step is started, the active steps change
depending on the starting method as described below.
• When the block START step makes a start using (Bm
,
Bm
)
• When a start is made using the block START instruction
(sBLm) of the SFC control instructions
• When a forced start is made using the block START/END
bit of the SFC information devices
• When any of the initial steps is specified using the step
control instruction (sBLm\Sn, sSn) of the SFC control
instructions
All initial steps become
active.
Only the specified step
becomes active.
(2) Transition processing performed when multiple initial steps become active
S8
S4
t4
S0
t0
S7
t7
S3
t3
S6
t6
S2
t2
S5
t5
S1
t1
If steps are selectively coupled in the block that has more than one active initial steps, the step
immediately after the coupling becomes active if any of the transition conditions immediately
before the coupling is satisfied.
In the above program example, step 8 (S8) becomes active when any of transition conditions
t4 to t7 is satisfied.
When, after the step immediately after the coupling (S8 in the above program example)
becomes active, another transition condition immediately before the coupling (any of t4 to t7 in
the above program example) is satisfied, reactivation processing is performed as a follow-up
function.
The processing, which will be performed when another transition condition is satisfied with the
step immediately after coupling being active, can be selected between STOP, WAIT and
TRANSFER in the "Operation mode at transition to active step (double step START)" (refer to
Section 4.7.6) in the block parameter setting of the SFC setting dialog box in the Tools menu.
The Basic model QCPU and Universal model QCPU does not allow the operation mode to be
selected.
It operates in the default "TRANSFER" mode.
(3) The operation of the initial steps with step attributes is the same as that of the other steps.
Refer to Section 4.2.4 to Section 4.2.7.

Mitsubishi Q Series Specifications

General

Brand	Mitsubishi
Model	Q Series
Category	Control Unit
Language	English