Class _icb: 16-bit capture unit

A class _icb 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:

• ATmega16U4/32U4 : counter3capture0

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:

Note Currently, only edge configuration is implemented for the synchronous method.

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

hwa( configure,   capture0,
 
     input,       pin_icp,           // FIXME: (pin,icp)
 
   [ 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,capture0,irq) ) ) {     // Read capture IRQ flag
  hw( clear,(counter0,capture0,irq) );                  // Clear capture IRQ flag
  hw( disable,(counter0,capture0,irq) );                // Disable capture IRQs
}