NEC mPD780852 Series, Preliminary User'S Manual

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Preliminary User’s Manual U14581EJ3V0UM00
CHAPTER 19 INTERRUPT FUNCTIONS
19.1 Interrupt Function Types
The following three types of interrupt functions are used.
(1) Non-maskable interrupt
This interrupt is acknowledged unconditionally even in the interrupt disabled state. It does not undergo priority
control and is given top priority over all other interrupt requests.
A standby release signal is generated.
One interrupt request from the watchdog timer is incorporated as a non-maskable interrupt.
(2) Maskable interrupts
These interrupts undergo mask control. Maskable interrupts can be divided into a high interrupt priority group
and a low interrupt priority group by setting the priority specify flag registers (PR0L, PR0H, PR1L).
High priority interrupts can be issued even if there are low priority interrupts. If two or more interrupts with the
same priority are simultaneously generated, each interrupt has a predetermined priority (see Table 19-1).
A standby release signal is generated.
Three external interrupt requests and sixteen internal interrupt requests are incorporated as maskable interrupts.
(3) Software interrupt
This is a vectored interrupt to be generated by executing the BRK instruction. It is acknowledged even in the
interrupt disabled state. The software interrupt does not undergo interrupt priority control.
19.2 Interrupt Sources and Configuration
A total of 21 interrupt sources exist among non-maskable, maskable, and software interrupts (see Table 19-1).