Intterupt not working...

Hi,

I'm using a timer and external interrupt to detect the pulse, i can set the timer to run for 5 secs and loop back. But the program cannot vector to the external interrupt. This is my interrupt configurations and routine.

;********************************************
;-----------INTERRUPTS CONFIGURATIONS--------
;********************************************
MOV IE,#8CH
MOV SWCINT,#000H
MOV EIE1,#000H
MOV EIE2,#000H
MOV EIP1,#000H
MOV EIP2,#000H
MOV IP,#08H

;****************************
;-Timer 1 Overflow Interrupt-
;****************************
T1_INT:    CLR TF1        ; Clear overflow flag
          MOV TH1,#0D0H
          MOV TL1,#0A0H
          RETI

;**********************
;-External Interrupt 1-
;**********************
EX_INT:    INC 40H         ; Increment 40H
          RETI

Does the input to the external interrupt need to be digital? Any advice would be nice... Thanks in advance.