Class _ica: 16-bit capture unit

A class _ica object is a 16-bit capture unit. It has the following relative objects:

• one counter, whose name is given by ( capture0, counter )
• one input pin, whose name is given by ( capture0, pin )

It is used in:

• ATtiny24/44/84 : counter1capture0
• ATmega48A/PA/88A/PA/168A/PA/328/P : counter1capture0

Instructions that do not produce C code

The HW_BITS() instruction returns the number of bits of the capture register:

#if HW_BITS( capture0 ) != 16
#  error A 16-bit capture unit is required!
#endif

Interrupts

The capture unit can trigger an anonymous IRQ when a capture event occurs.

HW_ISR( capture0 )
{
   // Process capture event
}

Actions

configure:

hw( configure, (counter0,capture0),
 
  [ input,     pin_icp      // NOT IMPLEMENTED YET
             | acmp0, ]
 
  [ edge,      falling
             | rising, ]
 
  [ filter,    on           // NOT IMPLEMENTED YET
             | off ] );

hwa( configure, counter0capture0,
 
   [ input,     pin_icp      // FIXME: (pin,icp)
              | acmp0, ]
 
   [ edge,      falling
              | rising, ]
 
   [ filter,    on
              | off ] );

read:

uint16_t capture = hw( read, capture0 );

write:

hw( write, capture0, value );

hwa( write, capture0, value );

Status

The capture event flag can be accessed through interrupt-related instructions:

if ( hw( read, (counter0,irq,capture0) ) ) { // Read capture IRQ flag
  hw( clear, (counter0,irq,capture0) );      // Clear capture IRQ flag
  hw( disable, (counter0,irq,capture0) );    // Disable capture IRQs
}