pit.cc.svn-base

德国Erlangen大学教学操作系统源码。

#include "machine/pit.h"

PIT::PIT()
	: cmd_port(PIT_ports::cmd1), data_port(PIT_ports::data10), _interval(PIT_Attrib::max_interval)
{
	interval(PIT_Attrib::max_interval);
}

PIT::PIT(int us)
	: cmd_port(PIT_ports::cmd1), data_port(PIT_ports::data10), _interval(us)
{
	interval(us);
}

PIT::PIT(PIT &pit)
	: cmd_port(PIT_ports::cmd1), data_port(PIT_ports::data10), _interval(pit._interval)
{
}

PIT::~PIT()
{
}

void PIT::interval(int us)
{
	if (us > PIT_Attrib::max_interval)
		us = PIT_Attrib::max_interval;
	else if (us < 0)
		us = 0;

	int counter = convert(us);
	_interval = us;

	cmd_port.outb(PIT_Attrib::timer0 | PIT_Attrib::low_high | PIT_Attrib::mode2 | PIT_Attrib::bin);
	data_port.outb(counter & 0xff);
	data_port.outb( (counter>>8) & 0xff);
}

int PIT::interval()
{
	return _interval;
}

int PIT::convert(int us) const
{
	int counter = PIT_Attrib::freqence/1000*us/1000;

	if(counter > PIT_Attrib::max_counter)
		counter = PIT_Attrib::max_counter;
	else if(counter < 1)
		counter = 1;

	return counter;
}