3.8 DF, DF/ (Leading Edge Differential, Trailing Edge Differential), DFI
(Leading Edge Differential (Initial Execution Type))
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Ladder diagram
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Outline of operation
Type of
instruction
Operation
DF
The DF instruction only generates output (differential output) for a single scan where the execution
condition changes from the OFF state to the ON state (i.e., rises).
DF/
The DF/ instruction only generates output (differential output) for a single scan where the
execution condition changes from the ON state to the OFF state (i.e., falls).
DFI
The DFI instruction only generates output (differential output) for a single scan where the
execution condition changes from the OFF state to the ON state (i.e., rises).
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Precautions for programming
● There are no restrictions on the number of times the differential instruction (DF, DF/, or DFI)
can be used.
● The differential instruction only detects changes in the ON/OFF states of a contact.
● The DF and DF/ instructions do not generate output if the execution condition is already
satisfied (i.e., ON state) when the operation mode is switched to RUN or the power is turned
on in the RUN mode.
● The DFI instruction generates output (differential output) for the first single scan even if the
execution condition is already satisfied when the RUN mode is initiated.
● If the execution condition can be already satisfied (i.e., on state) when the operation mode is
switched to RUN or the power is turned on in the RUN mode, output will not be obtained for
the first single scan by the DF instruction. Use the DFI instruction instead in this case.
● Be careful when using a differential instruction with an instruction (1 to 6 below) which
changes the order of instruction execution such as MC - MCE, JP - LBL.
1) MC - MCE instructions
2) JP - LBL instructions
3) LOOP - LBL instructions
4) CNDE instruction
3.8 DF, DF/ (Leading Edge Differential, Trailing Edge Differential), DFI
(Leading Edge Differential (Initial Execution Type))
3-12 WUME-FP7CPUPGR-12
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