483CHAPTER 21 INTERRUPT AND TEST FUNCTIONS21.1 Interrupt Function TypesThe following three types of interrupt functions are used.(1) Non-maskable interruptThis interrupt is acknowledged unconditionally even in the interrupt disabled status. It does not undergointerrupt priority control and is given top priority over all other interrupt requests.It generates a standby release signal.Non-maskable interrupt includes one interrupt request source from watchdog timer.(2) Maskable interruptsThese interrupts undergo mask control. Maskable interrupts can be divided into a high interrupt priority groupand a low interrupt priority group by setting the priority specify flag register (PR0L, PR0H, PR1L).Multiple high priority interrupts can be applied to low priority interrupts. If two or more interrupts with the samepriority are simultaneously generated, each interrupts has a predetermined priority (see Table 21-1).A standby release signal is generated.Maskable interrupt includes 7 external interrupt request sources and 13 internal interrupt request sources.(3) Software interruptThis is a vectored interrupt that occurs when the BRK instruction is executed. It is acknowledged even in adisabled state. The software interrupt does not undergo interrupt priority control.
