Mitsubishi Electric MELSEC FX3U Programming Manual page 817

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
Caution on using a rising/falling edge detection contact
When a rising/falling detection contact in LDP, LDF, ANDP, ANDF, ORP or ORF instruction is used in a state
relay, the contact whose status was changed while the state relay was OFF is detected when the state relay
turns ON the next time.
When it is necessary to immediately detect the rising edge or falling edge for a condition which may change
while a state relay is OFF, change the program as shown below:
S3
X013
X014
When the ON status is transferred to S70 at the falling edge of X013 and then X014 turns OFF after that, the
falling edge of X014 is not detected at this point because S3 is OFF. When S3 turns ON the next time, the
falling edge of X014 is detected.
Accordingly, when S3 turns ON the next time, the ON status is immediately transferred to S70.
SET S70
Change
35 SFC Program and Step Ladder
X013
M6
X014
M7
S3
M6
SET
M7
35.1 SFC Program
S70
815
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A
B