199 lines
6.4 KiB
C
199 lines
6.4 KiB
C
/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
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* Copyright (C) 2012 Benjamin Vernoux <titanmkd@gmail.com>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (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
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* GNU 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 License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @defgroup CM3_systick_defines Cortex-M SysTick Defines
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*
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* @brief <b>libopencm3 Defined Constants and Types for the Cortex SysTick </b>
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*
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* @ingroup CM3_defines
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*
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* @version 1.0.0
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*
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* @author @htmlonly © @endhtmlonly 2010 Thomas Otto <tommi@viadmin.org>
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*
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* @date 19 August 2012
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*
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* System Control Space (SCS) => System timer register support in the SCS.
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* To configure SysTick, load the interval required between SysTick events to
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* the SysTick Reload Value register. The timer interrupt, or COUNTFLAG bit in
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* the SysTick Control and Status register, is activated on the transition from
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* 1 to 0, therefore it activates every n+1 clock ticks. If you require a
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* period of 100, write 99 to the SysTick Reload Value register. The SysTick
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* Reload Value register supports values between 0x1 and 0x00FFFFFF.
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*
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* If you want to use SysTick to generate an event at a timed interval, for
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* example 1ms, you can use the SysTick Calibration Value Register to scale
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* your value for the Reload register. The SysTick Calibration Value Register
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* is a read-only register that contains the number of pulses for a period of
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* 10ms, in the TENMS field, bits[23:0].
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*
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* This register also has a SKEW bit. Bit[30] == 1 indicates that the
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* calibration for 10ms in the TENMS section is not exactly 10ms due to clock
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* frequency. Bit[31] == 1 indicates that the reference clock is not provided.
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*
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* LGPL License Terms @ref lgpl_license
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*/
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/**@{*/
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#ifndef LIBOPENCM3_SYSTICK_H
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#define LIBOPENCM3_SYSTICK_H
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#include <libopencm3/cm3/memorymap.h>
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#include <libopencm3/cm3/common.h>
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/** SysTick Control and Status Register (CSR).
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* Controls the system timer and provides status data.
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* Usage constraints: There are no usage constraints.
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* Configurations Always implemented.
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*/
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#define STK_CSR MMIO32(SYS_TICK_BASE + 0x00)
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/** SysTick Reload Value Register (RVR).
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* Reads or clears the value that will be loaded to the counter.
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* Usage constraints:
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* - Any write to the register clears the register to zero.
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* - The counter does not provide read-modify-write protection.
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* - Unsupported bits are read as zero
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* Configurations Always implemented.
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*/
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#define STK_RVR MMIO32(SYS_TICK_BASE + 0x04)
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/** SysTick Current Value Register (CVR).
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* Holds the current value of the counter.
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* Usage constraints: There are no usage constraints.
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* Configurations Always implemented.
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*/
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#define STK_CVR MMIO32(SYS_TICK_BASE + 0x08)
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/** SysTick Calibration Value Register(Read Only) (CALIB)
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* Reads the calibration value and parameters for SysTick.
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* Usage constraints: There are no usage constraints.
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* Configurations Always implemented.
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*/
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#define STK_CALIB MMIO32(SYS_TICK_BASE + 0x0C)
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/** @defgroup STK_CSR_VALUES STK_CSR Values
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* @{
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*/
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/** COUNTFLAG
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* Indicates whether the counter has counted to 0 since the last read of this
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* register:
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* 0 = Timer has not counted to 0
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* 1 = Timer has counted to 0.
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*/
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#define STK_CSR_COUNTFLAG (1 << 16)
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#define STK_CSR_CLKSOURCE_LSB 2
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/** CLKSOURCE: Clock source selection
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* for 0, SysTick uses the IMPLEMENTATION DEFINED external reference clock.
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* for 1, SysTick uses the processor clock.
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* If no external clock is provided, this bit reads as 1 and ignores writes.
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*/
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#define STK_CSR_CLKSOURCE (1 << STK_CSR_CLKSOURCE_LSB)
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/** @defgroup systick_clksource Clock source selection
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@ingroup CM3_systick_defines
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@{*/
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#if defined(__ARM_ARCH_6M__)
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#define STK_CSR_CLKSOURCE_EXT (0 << STK_CSR_CLKSOURCE_LSB)
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#define STK_CSR_CLKSOURCE_AHB (1 << STK_CSR_CLKSOURCE_LSB)
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#else
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#define STK_CSR_CLKSOURCE_AHB_DIV8 (0 << STK_CSR_CLKSOURCE_LSB)
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#define STK_CSR_CLKSOURCE_AHB (1 << STK_CSR_CLKSOURCE_LSB)
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#endif
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/**@}*/
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/** TICKINT: SysTick exception request enable */
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#define STK_CSR_TICKINT (1 << 1)
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/** ENABLE: Counter enable */
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#define STK_CSR_ENABLE (1 << 0)
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/**@}*/
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/** @defgroup STK_RVR_VALUES STK_RVR Values
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* @{
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*/
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/** RELOAD[23:0]: RELOAD value */
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#define STK_RVR_RELOAD 0x00FFFFFF
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/**@}*/
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/** @defgroup STK_RVR_VALUES STK_RVR Values
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* @{
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*/
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/** CURRENT[23:0]: Current counter value */
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#define STK_CVR_CURRENT 0x00FFFFFF
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/**@}*/
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/** @defgroup STK_CALIB_VALUES STK_CALIB Values
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* @{
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*/
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/** NOREF: NOREF flag
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* Bit31 => NOREF Indicates whether the IMPLEMENTATION DEFINED reference clock
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* is implemented:
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* 0 = The reference clock is implemented.
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* 1 = The reference clock is not implemented.
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* When this bit is 1, the CLKSOURCE bit of the SYST_CSR register is forced to
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* 1 and cannot be cleared to 0.
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*/
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#define STK_CALIB_NOREF (1 << 31)
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/** SKEW: SKEW flag
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* Bit30 => SKEW Indicates whether the 10ms calibration value is exact:
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* 0 = 10ms calibration value is exact.
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* 1 = 10ms calibration value is inexact, because of the clock frequency
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*/
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#define STK_CALIB_SKEW (1 << 30)
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/* Bits [29:24] Reserved, must be kept cleared. */
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/** TENMS Calibration value for 10ms.
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* Bit0 to 23 => TENMS Optionally, holds a reload value to be used for 10ms
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* (100Hz) timing, subject to system clock skew errors. If this field is zero,
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* the calibration value is not known.
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*/
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#define STK_CALIB_TENMS 0x00FFFFFF
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/**@}*/
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/* --- Function Prototypes ------------------------------------------------- */
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BEGIN_DECLS
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void systick_set_reload(uint32_t value);
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bool systick_set_frequency(uint32_t freq, uint32_t ahb);
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uint32_t systick_get_reload(void);
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uint32_t systick_get_value(void);
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void systick_set_clocksource(uint8_t clocksource);
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void systick_interrupt_enable(void);
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void systick_interrupt_disable(void);
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void systick_counter_enable(void);
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void systick_counter_disable(void);
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uint8_t systick_get_countflag(void);
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void systick_clear(void);
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uint32_t systick_get_calib(void);
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END_DECLS
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#endif
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/**@}*/
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