;====================================== Interrupt Vector Table ================     
    ORG 0x0000                         
    ajmp START                         ; RESET Vector
    
    ORG 0x0003
    ajmp EX0_isr                       ; External Interrupt 0 Vector
        
    ORG 0x000B
    ajmp T0_isr                        ; Timer 0 overflow Vector
    
    ORG 0x0013
    ajmp EX1_isr                       ; External Interrupt 1 Vector
    
    ORG 0x001B
    ajmp T1_isr                        ; Timer 1 overflow Vector
    
    ORG 0x0023
    ajmp Serial_isr                    ; Serial port (RI+TI) Vector
    
    ORG 0x0033
    ajmp AC_isr                        ; Analog Comparator Vector

;====================================== Interrupt Service Routines ============
START:      ljmp RUN_MCU               ; Goto START Program

; . . . 
; . . .
; . . . 
;

;====================================== RUN_MCU start everything ==============
RUN_MCU:                               ; FULL INITIALISATION of all SFRs
          //mov P0, #0x00              ; Port 0 does not exist on AT89S4051
          clr  IE_EA                   ; Disable any Interrupt Pending
          mov  SP, #STACK_START-1      ;
          mov  DPL, #0x00              ;
          mov  DPH, #0x00              ;
          mov  PCON, #0x00             ; SMOD1 SMOD0 PWMEN POF GF1 GF0 PD IDL
          mov  TCON, #0x00             ; TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
          mov  TMOD, #0x00             ; T1(G1 C/T1 M1 M0) T0(G0 C/T0 M1 M0)
          mov  TL0, #0x00              ;
          mov  TL1, #0x00              ;
          mov  TH0, #0x00              ;
          mov  TH1, #0x00              ;
          mov  CLKREG, #0x00           ; - - - - - - PWDEX X2
          mov  P1, #0xFF               ; Write 1's = Tristate Port Pins at P1
          mov  ACSR, #0x00             ; - - - CF CEN CM2 CM1 CM0
          mov  SCON, #0x00             ; SM0/FE SM1 SM2 REN TB8 RB8 TI RI
          mov  SBUF, #0x00             ; zero to Serial Buffer (NULL)
          //mov P2, #0x00              ;  Port 2 does not exist on AT89S4051
          mov  IE, #0x00               ; EA EC - ES ET1 EX1 ET0 EX0
          mov  SADDR, #0x00            ; Slave Address (ussualy not used)
          mov  P3, #0xFF               ; Write 1's = Tristate Port Pins at P3
          mov  IPH, #0x00              ; - PCH - PSH PT1H PX1H PT0H PX0H
          mov  IP, #0x00               ; - PC  - PS  PT1  PX1  PT0  PX0
          mov  SADEN, #0x00            ; Slave Address Mask (us.not used)
          mov  PSW, #0x00              ; Cy Ac F0 RS1 RS0 OV UF P
          mov  ACC, #0x00              ; zero to Accumulator
          mov  B, #0x00                ; zero to B Register 

iRam_clear: clr  A                     ; Clear all iRAM bytes 00h-FFh
          mov  R0, #0xFF               ; 
iRam_00:  mov  @R0, A                  ;
          dec  R0                      ;
          cjne R0,#0, iRam_00          ;   
          
          ljmp main                    ;