Block Start/End Bit - Mitsubishi Electric MELSEC-Q Series Programming Manual

Block START/END bit

The block START/END bit is used to confirm the active status of the specified block by a sequence program or the test
operation of the peripheral device.
It can also be used as a device to forcibly start or forcibly end the specified block.
• Operation of block START/END bit
The block START/END bit turns ON when the corresponding block starts.
The block START/END bit remains ON while the corresponding block is active.
The block START/END bit turns OFF when the corresponding block becomes inactive.
The block START/END bit remains OFF while the corresponding block is inactive.
• When the corresponding block is inactive, it can be started independently by forcibly turning ON the block START/END bit.
While the corresponding block is active, the processing of the corresponding block can be forcibly ended by forcibly turning
OFF the block START/END bit. The block START/END bit can also be turned ON/OFF in the test mode of the peripheral
device.
• When a forced OFF is executed by the block START/END bit, and the block in question becomes inactive, processing will
occur as follows:
Execution of the block in question will stop together with all outputs from the step which was being executed.
(Devices switched ON by the SET instruction will not switch OFF.)
If another block is being started by the block START step in the corresponding block, the corresponding block stops.
However, the start destination block remains active and continues processing.
To also end the start destination block simultaneously, the block START/END bit of the start destination must also be turned
OFF.
• A block which has been forcibly deactivated is restarted as shown below.
Relevant Block
Block 0 When the START condition of block 0 is "Auto START ON" in the
SFC setting of the PLC parameter dialog box.
When the START condition of block 0 is "Auto START OFF" in
the SFC setting of the PLC parameter dialog box.
Other than block 0
4 SFC PROGRAM CONFIGURATION
106
4.5 SFC Information Devices
Restart Status
Operation is restarted from the initial step following END step
processing.
The block is deactivated after END step processing, and processing is
restarted from the initial step when another START request occurs for
that block.