Hello vinay,
The XIRQ pin is level-sensitive. It produces an interrupt request as long as you keep it low. For using this as a regular interrupt pin, there needs to be some kind of handshake taking place between the external hardware which asserts/de-asserts the signal on the XIRQ pin and the software (= the XIRQ ISR).
If the interrupt is de-asserted before the XIRQ ISR is entered, you get either nothing (i.e. the event is lost) or you get a spurious interrupt (i.e. the vector address is unknown by the time the CPU starts interrupt processing).
The same applies to the IRQ pin, in level-sensitive mode.
So, just putting "pulses" on the XIRQ pin is not going to work reliably.
HTH,
MJW