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