1. You should move your main routine after all interrupt vectors. Put it after 0100h.

2. Never loop inside an ISR, use looping in your main. Otherwise you will have stack overflow problem.

3. You check DPH and DPL, but I cannot see where you increase or decrease these two values.

4. Try not to use DPH and DPL for looping, you need it to access external memory, try to use a memory location or a register set.

5. Remember to put reti on all other unused interrupt vector.

6. Did you tried to write a LED blinking routine using timer interrupt? If not, I think you should do it first.

Good Luck.
Lawrence