Block Start And End; Block Start Methods - Mitsubishi Electric MELSEC-Q Series Programming Manual

6.2

Block START and END

This section describes the block START and END.

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.
: Usable, : Unusable
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
6 SFC PROGRAM EXECUTION
160
6.2 Block START and END
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 at
each of the SFC program blocks.
Using an SFC control instruction, a specified block is
forcibly started from an SFC program step (operation
output), or from another sequence program.
• When specified block is executed from its initial step:
• When specified block is executed from a specified
step:
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.
Remarks
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.
• 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.
Convenient when starting an error reset
processing block at error detection, etc., and
for executing interrupt 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.
Block 0 Other
than
Block 0
 
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