I seem to remember that if you use I/O interrupts on X0-X7 there are special memory areas in the D8000 range that give you the input pulse duration as well as immidiate I/O update, you could use this in conjunction with the PWM instruction to output pulses by parameterising the PWM with pulse width in ms & number of pulses i.e. 1 so in effect it should give the Y output the same pulses as the X input, bear in mind the PWM instruction does not work on the simulator & obviously you need a FX3 with transistor outputs.
I cannot find it now but I also seem to remember there was some way of directly accessing the X/Y I/O i.e. immidiate update of physical inputs & outputs, but I have no idea if that will work on FX range of PLC's I believe it was some suffix on the I/O number like DX000 DY001 but I know it is not that just tried it but I'm certain I have seen it somewhere in the past.
Perhaps read this manual for high speed interrupts & PWM look at page 823 it shows the D8079 as the pulse period for X0 that is set when the interrupt is run
THE PWM instruction takes two input parameters i.e. pulse width in ms & number of pulses, never tried it but perhaps use that N1 would be D8079 & N2 would be 1, it's a guess, but perhaps in conjunction with the I/O interrupts it will give you a pulse every time X0 goes true & the last pulse width so sort of reflecting the input pulses back out to the output