Negative edge trigger interrupt (assembler)

COUNT EQU 9217 ;For the crystal oscillator of 11.0592, the delay is 10ms
LED1 EQU P1.1
LED2 EQU P1.3 ;Used as the display of external interrupt 0 
;
               ORG 0000H
               LJMP RESET ;Jump to the initialization program
               ORG 0003H ; INT0 (external interrupt 0)
               LJMP INT_ET0 ;Jump to the external interrupt 0 service program (this program interrupt is entered from here)  
               ORG 000BH ;TIMER0 (timer/counter T0)
               LJMP INT_TIMER0 ;Jump to the timer/counter interrupt service program
               // ORG 0013H ;External interrupt 1   
               // RETI ;Interrupt return instruction
               // ORG 001BH ;TIMER1 (timer/counter T1)
               // RETI
               // ORG 0023H ;Serial port interrupt
               // RETI
;
               ORG 0030H
RESET: MOV R0,#00H
               DJNZ R0,$ ;At the beginning, a small delay is performed to prepare various working registers
  
              SETB LED1
              SETB LED2
  
;Set timer interrupt 
             MOV TMOD,#00000001B
             MOV TH0,#HIGH(65536-COUNT)
             MOV TL0,#LOW(65536-COUNT)
             //MOV TH0,#(65536-COUNT)/256;Get the high eight bits of data
             // MOV TL0,#255 ;Get the bottom five bits (the largest)
             CLR TF0 ;Clear the overflow flag first
             SETB TR0 ;Start timing
             SETB ET0 ;ET0 is the overflow interrupt enable bit of timer/counter T0
;Set external interrupt 0
             SETB IT0 ;Set external interrupt 0 as jump trigger mode
             CLR IE0
             SETB EX0                                                                                                                                             
             SETB EA
             MOV IP,#00000001B; Set PX0 to high priority interrupt (external interrupt 0) 
             MOV R1,#00H; Used as timer accumulator

LOOP: SJMP LOOP ;Wait here
;
;IE0=1

INT_ET0://CLR LED2
            CPL TR0
            //CPL LED1
            ACALL DELAY
            CLR IE0
            CPL LED2
            RETI

;TF0=1  
INT_TIMER0:
            INC R2 ;Increment R1 by one
            CLR TF0 ;CLEAR TF0 AGAIN
            MOV TH0,#(65536-COUNT)/256;Get the high eight bits
            MOV TL0,#255 ;Get the bottom five bits (the maximum)

           CJNE R2,#10,L0; If not equal, transfer instruction, this number can be adjusted
           CPL LED1; Invert instruction
           MOV R2, #00H
L0: RETI

;Delay subroutine, 12M crystal delay is about R4
DELAY: ;Approximate value: 2us*256*256*2=260ms, can also be considered as 250ms
           PUSH PSW ;Site protection instruction (sometimes it can be omitted)
           MOV R4,#4   
L3: MOV R2 ,#00H
L1: MOV R3 ,#00H
L2: DJNZ R3 ,L2 ;Innermost loop: (256 times) 2 cycle instructions (R3 minus one, if greater than 1, turn to L2) 
           DJNZ R2 ,L1 ;Middle loop: 256 times
           DJNZ R4 ,L3 ;Outer loop: 2 times
 
          POP PSW
          RET

          END