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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
35 SFC Program and Step Ladder
35.1 SFC Program
2. Procedure using a pulse contact instruction (M2800
to M3071)
By using an auxiliary relay M2800 to M3071 in a rising/falling
edge detection instruction (LDP, LDF, ANDP, ANDF, ORP or
ORF), the ON status can be efficiently transferred by the same
signal.
When M2800 or later is specified as a device in a rising/falling
edge detection instruction, only the first rising/falling edge
detection instruction after a coil instruction is executed.
Accordingly, when X001 is set to ON, only the transfer condition
in a state relay currently in the ON status is ON during one
operation cycle, and then the ON status is transferred to the
next state relay.
*1. It is alright to program a device number used in LD, LDI,
OR or ORI instructions after a corresponding coil in the ladder block. However, if a same device number is
programmed in LDP, LDF, ANDP, ANDF, ORP or ORF instruction, the priority is given to such an instruction
and the transfer condition is not effective.
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:
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.
51
50
X001
0
2
3
TRAN
Ladder block
SFC block
(Transfer input)
M2800
M2800
M2800
1
M2800
TRAN
M2800
TRAN
M2800
*1
X013
S3
X014
SET S70
Change
X013
S3
SET S70
M7
M6
M6
M7
X014