External IRQ interrupt on HCS08

Freescale’s HCS08 microcontrollers have two external interrupt sources: the IRQ interrupt and the keyboard interrupt. The IRQ pin can be configured to generate interrupts on falling or rising edges or on high/low logic states.

When a configured edge or level is detect on IRQ, the IRQF flag is set and can generate an interrupt. That interrupt source can also be used to wakeup the chip from a low-power mode.

The following example, from my HCS08 Unleashed book, demonstrates how to use that interrupt on the MC9S08QG8 microcontroller (using Freescale’s DEMOQG8 board).

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