External Interrupt Function - Fujitsu MB90895 Series Hardware Manual

12.4.1

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 or RX
pin.
I External Interrupt Function
• When the signal (edge or level) set in the detection level setting register is detected in the DTP/external
interrupt pin or RX pin, the interrupt request flag bit (EIRR: ER) in the DTP/external interrupt request
register is set to "1".
• If the interrupt request enable bit in the DTP/external interrupt enable register is enabled (ENIR: EN =
1) and the interrupt request flag bit set to "1", the interrupt is implemented to the interrupt controller.
• An interrupt request is generated when the interrupt controller prefers the interrupt request to other
requests.
• If the level of an interrupt request (ICR: IL) is higher than that of the interrupt level mask bit (TLM) in
the processor status (PS) 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 (EIRR: ER) is set to "1", regardless of the setting of the DTP/external
interrupt request enable bit (ENIR: EN).
• When the interrupt processing is started, clear the DTP/external interrupt request flag bit
that caused the interrupt. 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.
CHAPTER 12 DTP/external interrupt
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