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Figure 18.6-2 DTP/external Interrupt Cause and Interrupt Request when the Output of Interrupt Requests
DTP/external interrupt
cause (when the H level
is detected)
Interrupt request to the
interrupt controller
●
Notes about interrupts
When the external interrupt function is used, control cannot return from the interrupt processing routine if
the external interrupt request flag bit is "1" and the output of interrupt requests is enabled. In the interrupt
processing routine, the external interrupt request flag bit must be cleared. (When the DTP function is used,
2
EI
OS automatically clears the bit.) For level detection, the external interrupt request flag bit is set again as
soon as it is cleared if the level assumed as an interrupt cause continues to be input. Either disable the
output of interrupt requests or remove the interrupt cause, if required.
CHAPTER 18 DTP/EXTERNAL INTERRUPT CIRCUIT
is enabled
H level
Removal of the interrupt cause
Request becomes inactive when
cause flip-flop is cleared
531
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