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Chapter 3 Interrupts
III - 16
Control Registers
3-2-2 Interrupt Control Registers
The interrupt control registers include the maskable interrupt control registers (xxxICR) and the non-
maskable interrupt control register (NMICR).
■Non-Maskable Interrupt Control Register (NMICR address: x'03FE1')
The non-maskable interrupt control register (NMICR) stores the non maskable interrupt request. When
the non-maskable interrupt request is generated, the interrupt is accepted regardless of the interrupt
mask level (IMn) of PSW. The hardware then branches to the address stored at location x'04004' in the
interrupt vector table. The watchdog timer overflow interrupt request flag (WDIR) is set to "1" when the
watchdog timer overflows. The program interrupt request flag (PIR) is set to "1" when the undefined
instruction is executed.
WDIR
Watchdog interrupt request flag
0
Interrupt request generated
7
0
NMICR
WDIR Reserved
(At reset : -----000)
1
No interrupt request
PIR
PIR
Program interrupt request flag
0
Interrupt request generated
1
No interrupt request
1
2
34
5
6
Reserved
Always set to "0".
-
-
-- -
Figure 3-2-1 Non-Maskable Interrupt Control Register
(NMICR:x'03FE1', R/W)
On this LSI, when undefined instruction is decoded, the program interrupt request flag (PIR)
is set to "1", and the non-maskable interrupt is generated.
If the PIR flag setup is confirmed by the non-maskable interrupt service routine, the reset via
the software is recommended, When software reset, the reset pin (p27) outputs "0".
Once the WDIR flag becomes "1" after non-maskable interrupt happens, only the program
can clear it to "0".