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CHAPTER 17 DTP/EXTERNAL INTERRUPTS
17.4.1 External Interrupt Function
The DTP/external interrupt has an external interrupt function for generating an interrupt
request by detecting the signal (edge or level) in the DTP/external interrupt pin.
■ External Interrupt Function
• When the signal (edge or level) set in the detection level setting register is detected in the DTP/external
interrupt pin, the interrupt request flag bit in the DTP/external interrupt factor register (EIRR1:ER) is set
to "1".
• If the interrupt request enable bit in the DTP/external interrupt enable register is enabled (ENIR1:EN =
1) with the interrupt request flag bit set to "1", the interrupt request generation is posted to the interrupt
controller.
• If an interrupt request is preferred to other interrupt request by the interrupt controller, the interrupt
request is generated.
• If the level of an interrupt request (ICR:IL) is higher than that of the interrupt level mask bit in the
condition code register (CCR:ILM) and the interrupt enable bit is enabled (PS:CCR:I = 1), the CPU
performs interrupt processing after completion of the current instruction execution and branches to
interrupt processing.
• At interrupt processing, set the corresponding DTP/external interrupt request flag bit to 0 and clear the
DTP/external interrupt request.
Notes:
• When the DTP/external interrupt start factor is generated, the DTP/external interrupt request flag bit
(EIRR1:ER) is set to "1", regardless of the setting of the DTP/external interrupt request enable bit
(ENIR1:EN).
• When the interrupt processing is started, clear the DTP/external interrupt request flag bit that caused the
start factor. Control cannot be returned from the interrupt while the DTP/external interrupt request flag
bit is set to "1". When clearing, do not clear any flag bit other than the accepted DTP/external interrupt
factor.