Continuous Transition Bit - Mitsubishi Electric MELSEC-Q Series Programming Manual

Continuous transition bit

The continuous transition bit specifies whether the operation output of the next step will be executed in the same scan or not
when the transition condition is satisfied.
• There are two types of SFC program transition processing: "with continuous transition" and "without continuous transition".
The user specifies either of them by turning ON/OFF the continuous transition bit.
Processing
Continuous transition ON
(Continuous transition bit: ON)
Continuous transition OFF
(Continuous transition bit: OFF)
Ex.
Sample program processing
• A continuous transition can be designated for individual blocks by the continuous transition bit ON/OFF setting, or for all
blocks using the batch setting special relay. As indicated below, whether a continuous transition is executed or not changes
depending on the combination of the continuous transition bit and the special relay that sets "whether continuous transition
of all blocks is executed or not" (SM323).
SM323 status
ON
OFF
The tact time can be shortened by setting "with continuous transition".
This resolves the problem of waiting time from when the transition condition is satisfied until the operation
output of the transition destination step is executed.
However, when "with continuous transition" is set, the operations of the other blocks and sequence program
may become slower.
4 SFC PROGRAM CONFIGURATION
114
4.5 SFC Information Devices
Description
When the transition conditions at contiguous steps are satisfied, all the steps transition conditions will be executed at
once within a single scan.
Steps are executed in a 1-step-per-scan format.
• Continuous transition ON
When the corresponding block becomes active, the processings of all steps are executed in the same scan, and end
step processing is performed to deactivate the block.
• Continuous transition OFF
When the corresponding block becomes active, steps are executed in a 1-step-per-scan format, and end step
processing is performed in the third scan to deactivate the block.
Continuous Transition Bit Status
Continuous transition bit OFF
No continuous transition bit setting
Continuous transition bit ON
Continuous transition bit OFF
No continuous transition bit setting
Continuous transition bit ON
SFC Program Operation
Operation occurs without continuous transition
Operation occurs with continuous transition
Operation occurs without continuous transition
Operation occurs with continuous transition