
B-63983EN/02 4.LADDER LANGUAGE
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4.8.2 DIFD (Falling Edge Detection: SUB 58)
The DIFD instruction set the output signal to 1 for one scanning period
on a falling edge of the input signal.
Format
Fig. 4.8.2 shows the ladder format and Table 4.8.2 shows the
mnemonic format.
DIFD
SUB 58
Falling edge
number
CT
OUT
¡¡¡¡
Fig. 4.8.2 Format of DIFD instruction
Table 4.8.2 Mnemonic of DIFD instruction
Mnemonic format Status of operation result
Step
number
Instruction
Address
No.
Bit No. Remarks ST3 ST2 ST1 ST0
1RD ¡¡¡¡ .¡ ACT ACT
2 SUB 58 DIFD instruction
3(PRM) ¡¡¡¡ Falling edge number
4WRT ¡¡¡¡ .¡ OUT OUT
Control conditions
(a) Input signal (ACT)
On a falling edge (1→0) of the input signal, the output signal is set
to 1.
Detection result
(a) Output signal (OUT)
The output signal level remains at 1 for one scanning period of the
ladder level where this functional instruction is operating.