The problem of the eight-pin microcontroller STC15F104E external interruption

A few days ago,I used the eight-pin microcontroller STC15F104E to make an external interruption. Falling the edge triggers, but when the frequency of the trigger signal was too high(> 6HZ), there would be no interruption...
Have anyone used this microcontroller? Does this microcontroller itself have any problem?

EX0 = 1; // open external interrupt
IT0 = 1; // falling edge trigger

/ **********************************
External interrupt service routine
*********************************** /
void OutServy (void) interrupt 0
GPIO_jdq = 0;
temp = 0;
GPIO_LED = ~ GPIO_LED; (frequency is too high the led not jump, that did not enter the interruption)
TR0 = 1;