AT89C2051 EX1 Interrupt Triggering Automatically in Mode 1—How to Fix?

I am making a timer with atmel at89c2051. In which I have used all 4 interrupts. Tr0, tr1,ex0 and ex1. My problem is the ex1 interrupt is triggering automatically. If it is removed no problem.

But it is required. PL. Help me to solve this issue. I am using mode 1.

Sethumadhavan