[?]: Time Delay Interrupt greater 10ms

[waqas_here]

Hey i am having some problem while working with Time delay interrupt.
It's working fine when the delay time is around 10ms.
However for greater time delay it doesn't work.
Plz tell me what is the delay time limitation for it.

Also i want to generate square wave of 50% duty cycle of variable frequency. How can i do it.
Frequency range from 0Hz to 5KHz max.