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19 BUILT-IN I/O FUNCTION
19.5 FX3-Compatible Pulse Catch Function
Displayed items
Parameters are enabled when the CPU module is powered ON or after a reset.
Operation of FX3-compatible pulse catch function
Operation of the FX3-compatible pulse catch function is explained below.
Operation of FX3-compatible pulse catch function
When the status of the input (X0 to X7) changes OFFON after execution of the EI instruction, a special relay (SM8170 to
SM8177) is immediately set to ON by interrupt processing. Pulse catch operates even when an input interrupt is also set in
duplicate with other functions. Note, however, that the pulse catch must be set with parameters.
■Examples of program
When the status of the X0 changes OFFON after execution of the EI instruction, SM8170 is immediately set to ON by
interrupt processing. To capture input again, turn X2 ON to reset SM8170. (X0 is assumed to be set with parameters.)
■Operation diagram
An operation diagram of the above program example is shown below.
Cautions when using the FX3-compatible pulse catch function
• The FX3-compatible pulse catch function operates only when “Interrupt (Rising)” or “Interrupt (Rising) + Pulse Catch” is set
with parameters.
• To capture input again, the special relay that is set must be reset by the program. Accordingly, new input cannot be
captured until the special relay that is set is reset.
• The special relays for FX3-compatible pulse catch are cleared at STOPRUN and a reset.
• The FX3-compatible pulse catch function is executed regardless of the operations of the special relays for disabling
interrupts.
Item Description Setting range Default
General/Interrupt/Pulse
Catch Setting
Set the function to be used.
Set to “Interrupt (Rising)” or “Interrupt (Rising) + Pulse Catch”.
• General-purpose Input
• Interrupt (Rising)
• Interrupt (Falling)
• Interrupt (Rising + Falling)
• Interrupt (Rising) + Pulse Catch
General-purpose
Input
Reset input
RST
SM8170
X2
SM8170
Y0
X0
Y2
EI
It can be simultaneously used in a program.
SM8170
X0 (input)
X2 (reset)
Input pulse width
EI