A class _pxa object is a pin change interrupt controller.

It is used in:

ATtiny24/44/84 : pcic0, pcic1
ATtiny25/45/85 : pcic0
ATmega48A/PA/88A/PA/168A/PA/328/P : pcic0, pcic1, pcic2

Interrupts

Class _pxa objects can trigger the following IRQs as soon as the state of one of its monitored pins changes:

pcic0: monitored pin change event

Actions

enable, disable, turn select which pins are monitored (one or several at once):

hw|hwa( enable, pcic0, (porta,0) );

hw|hwa( disable, pcic0, (porta,0) );

hw|hwa( turn, pcic0, (porta,0), on | off );

FIXME: object should be '(pcic0,(porta,0))'

Status

The pin change IRQ flag and the enable bit can be accessed through interrupt-related instructions:

if ( hw( read, (pcic0,irq) ) ) {     // Read pin change flag
  hw( clear, (pcic0,irq) );          // Clear pin change flag
  hw( disable, (pcic0,irq) );        // Disable pin change IRQ
}

Registers

Hardware registers:

msk: mask of monitored pins

Logical registers:

ie: pin change IRQ mask
if: pin change IRQ flag