Fujitsu F2MC-8FX Hardware Manual page 326

CHAPTER 18 EXTERNAL INTERRUPT CIRCUIT
Interrupt processing
1) Clear the interrupt request flag. (EIC:EIR0 = 0)
2) Process any interrupt.
Note:
The external interrupt input is also used as an I/O port. Therefore, when it is used as the external
interrupt input, the corresponding bit in the port direction register (DDR) must be set to "0" (input).
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