R8C datasheet(173/199 Pages) RENESAS

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R8C/10 Group

19. Usage Notes

Rev.1.20 Jan 27, 2006

page 163 of 180

REJ09B0019-0120

19.2 Interrupt

19.2.1 Reading Address 0000016

Do not read the address 0000016 by a program. When a maskable interrupt request is acknowledged,

the CPU reads interrupt information (interrupt number and interrupt request level) from 0000016 in the

interrupt sequence. At this time, the acknowledged interrupt IR bit is set to “0”.

If the address 0000016 is read by a program, the IR bit for the interrupt which has the highest priority

among the enabled interrupts is set to “0”. This may cause a problem that the interrupt is canceled, or

an unexpected interrupt is generated.

19.2.2 SP Setting

Set any value in the SP before an interrupt is acknowledged. The SP is set to “000016” after reset.

Therefore, if an interrupt is acknowledged before setting any value in the SP, the program may run out

of control.

19.2.3 External Interrupt and Key Input Interrupt

________

Either an “L” level or an ”H” level of at least 250ns width is necessary for the signal input to the INT0 to

________

_____

INT3 pins and KI0 to KI3 pins regardless of the CPU clock.

19.2.4 Watchdog Timer Interrupt

Reset the watchdog timer after a watchdog timer interrupt is generated.

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