Mitsubishi Electric MELSEC FX3U Programming Manual page 870

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
When using the pulse catch function at 5 µs or when receiving a pulse whose response frequency is
*1.
50 k to 100 kHz using a high speed counter, perform the following:
-Make sure that the wiring length is 5 m or less.
-Connect a bleeder resistor of 1.5 kΩ (1 W or more) to the input terminal, and make sure that the load
current of the open collector transistor output in the counterpart equipment is 20 mA or more
including the input current in the main unit.
3. Cautions on use
1) When receiving an input again, it is necessary to reset the device which was once set using a program.
Accordingly, until a device is reset, a new input cannot be received.
2) When it is necessary to receive continuous short pulses (input signals), use the external input interrupt
function or high speed counter function.
3) A filter adjustment program is not required.
4) The pulse catch function is executed regardless of the operations of the special auxiliary relays M8050 to
M8055 for respectively disabling interrupts.
868
36 Interrupt Function and Pulse Catch Function
36.7 Pulse Catch Function [M8170 to M8177]