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/*
* Copyright (C) 2014 René Kijewski <rene.kijewski@fu-berlin.de>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @brief Interfacing with the PIT.
*
* The core of the x86 port only uses the RTC for the hwtimer.
* Application developers are free to use this module.
* Be aware of portability issues.
*
* You most likely want to use the xtimer interface instead.
*
* @ingroup x86-irq
* @{
* @file
* @author René Kijewski <rene.kijewski@fu-berlin.de>
*/
#ifndef CPU__X86__PIT__H__
#define CPU__X86__PIT__H__
#include <stdbool.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
#define PIT_CHANNEL_0_PORT (0x40) /**< Channel 0 */
#define PIT_CHANNEL_1_PORT (0x41) /**< Channel 1, DO NOT USE */
#define PIT_CHANNEL_2_PORT (0x42) /**< Channel 2, do not use if you can help it */
#define PIT_COMMAND_PORT (0x43)
#define PIT_ACCESS_MODE_LATCH_COUNT (0 << 4)
#define PIT_ACCESS_MODE_LO_BYTE (1 << 4)
#define PIT_ACCESS_MODE_HI_BYTE (2 << 4)
#define PIT_ACCESS_MODE_LO_HI (3 << 4)
#define PIT_INTERRUPT_ONTERMINAL_COUNT (0 << 1) /**< */
#define PIT_ONE_SHOT (1 << 1) /**< */
#define PIT_RATE_GENERATOR (2 << 1) /**< */
#define PIT_SQUARE_WAVE (3 << 1) /**< */
#define PIT_SOFWARE_TRIGGERED_STROBE (4 << 1) /**< */
#define PIT_HARDWARE_TRIGGERED_STROBE (5 << 1) /**< */
#define PIT_MIN_HZ (19)
#define PIT_MAX_HZ (1193181)
/**
* @brief Initialize the Programmable Interval Timer.
*
* This function is called during initialization by x86_startup().
* You must not call this function on your own accord.
*/
void x86_init_pit(void);
/**
* @brief Reads the current value of the of the channel.
* @param channel Channel (1, 2, or 3) to read from.
* @returns Current value of the channel.
*
* Channel 1 is the only channel that you should access.
*
* Channel 2 might be absent on current systems.
* It was never free to use for the OSes.
* Never access this channel!
*
* Channel 3 was originally intended to be used by the sound card.
* It's free to use, but you probably shouldn't.
*/
uint16_t x86_pit_read(unsigned channel);
/**
* @brief Sets the speed and operation mode of a channel.
* @param channel Channel (1, 2, or 3) to set.
* @param mode Action on overflow.
* @param max After how many ticks the timer should overflow.
*
* See x86_pit_read() for considerations about the channel.
*
* The timer has a speed of 1193181hz.
* That value was convinient for hardware vendors,
* but has only the quite useless prime factors 3, 11, 19, and 173.
* That hurts the usefulness severly.
*/
void x86_pit_set2(unsigned channel, unsigned mode, uint16_t max);
/**
* @brief Convenience wrapper for x86_pit_set2().
* @param hz After how how long the timer should overflow.
* @returns true iff the value of hz was sane.
*
* See x86_pit_set2() for a more detailed explanation.
* max will be set to 1193181 / hz.
* That means hz has to be a value between 19 and 1193181.
*
* Beware: the 1,193,163 different values for hz will only render 2,165 different values for max.
*/
bool x86_pit_set(unsigned channel, unsigned mode, unsigned hz);
#ifdef __cplusplus
}
#endif
#endif
/** @} */
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