@ Timer O Intr Fetch code at 0x000B

000B: LJMP SWT_T0_ISR

   - - - 

SWT_T0_ISR:
      PUSH  PSW
      JNB   PSW.1, LDR_T0_ISR     ;(i.e. F1 flag)
      POP   PSW
      LJMP  APP_OFFSET+0x000B     ;branch to app interrupt vector table
LDR_T0_ISR:
      PUSH  ACC
        ....          ;do loader timer functions
      POP   ACC
      POP   PSW
      RETI

   - - -

APP_OFFSET+0x00:
      LJMP  STARTUP
APP_OFFSET+0x0B:
      LJMP  APP_TIMER_0_ISR