Block Start And End - Mitsubishi Q series Programming Manual

6 SFC PROGRAM EXECUTION

6.2 Block START and END

6.2.1 Block START methods
The block START methods during SFC program execution are described below.
As shown below, there are several block START methods. Choose the method which is most
suitable for the purpose at hand.
START Method
Auto START using PLC
parameter
Block START by SFC
diagram symbol
Block START by SFC
control instruction
Block START by SFC
information device
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Operation Description
• By setting the "start condition" to "block
0 Auto START" in the SFC setting of the
PLC parameter dialog box, block 0 is
automatically started at an SFC program
start, and processing is executed from
the initial step.
• Another block is started by the block
START steps (Bm , Bm ) at each of
the SFC program blocks.
Transition condition
satisfied
n
Bm
Block m is started.
Block No. to be started
• Using an SFC control instruction, a
specified block is forcibly started from an
SFC program step (operation output), or
from another sequence program.
(1) When specified block is executed
from its initial step:
Condition
sBLm
(2) When specified block is executed
from specified step:
Condition
sBLm\Sn
m is the block No., n is the step No.
• The corresponding block is activated by
forcibly turning ON the "block
START/END bit", which was set to each
block as the SFC information device, in
the program or peripheral
device.information register.
• Convenient when block 0 is
used as a control block, a
preprocessing block, or a
constant monitoring block, for
example.
• Convenient when the
sequence control is clear as
in automatic operation.
m
• There are 2 types of block
START:
The START source step
remains active until the
START destination block is
ended.
The START source transition
occurs without waiting for the
START destination block to
be ended (SFC diagram
symbol: Bm ).
• Convenient when starting an
error reset processing block
at error detection, etc., and
for executing interrupt
m is the block No.
processing, for example.
• Convenient for debugging
and test operations in 1-block
units because the block can
be started from a peripheral
device without requiring a
program.
Remarks Block 0
: Usable,
MELSEC-Q
Other than
Block 0
: Unusable
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