Systick_api

Functions
void	SysTickEnable (void)
void	SysTickDisable (void)
void	SysTickIntRegister (void(*pfnHandler)(void))
void	SysTickIntUnregister (void)
void	SysTickIntEnable (void)
void	SysTickIntDisable (void)
void	SysTickPeriodSet (uint32_t ui32Period)
uint32_t	SysTickPeriodGet (void)
uint32_t	SysTickValueGet (void)

Detailed Description

Function Documentation

void SysTickDisable

(

void

)

Disables the SysTick counter.

This function stops the SysTick counter. If an interrupt handler has been registered, it is not called until SysTick is restarted.

Returns

None.

Definition at line 94 of file systick.c.

References HWREG, NVIC_ST_CTRL, and NVIC_ST_CTRL_ENABLE.

Referenced by scheduler_reschedule().

{
    //
    // Disable SysTick.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_ENABLE);
}

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void SysTickEnable

(

void

)

Enables the SysTick counter.

This function starts the SysTick counter. If an interrupt handler has been registered, it is called when the SysTick counter rolls over.

Note

Calling this function causes the SysTick counter to (re)commence counting from its current value. The counter is not automatically reloaded with the period as specified in a previous call to SysTickPeriodSet(). If an immediate reload is required, the NVIC_ST_CURRENT register must be written to force the reload. Any write to this register clears the SysTick counter to 0 and causes a reload with the supplied period on the next clock.

Returns

None.

Definition at line 75 of file systick.c.

References HWREG, NVIC_ST_CTRL, NVIC_ST_CTRL_CLK_SRC, and NVIC_ST_CTRL_ENABLE.

Referenced by scheduler_reschedule(), and systick_init().

{
    //
    // Enable SysTick.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_CLK_SRC | NVIC_ST_CTRL_ENABLE;
}

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void SysTickIntDisable

(

void

)

Disables the SysTick interrupt.

This function disables the SysTick interrupt, preventing it from being reflected to the processor.

Returns

None.

Definition at line 193 of file systick.c.

References HWREG, NVIC_ST_CTRL, and NVIC_ST_CTRL_INTEN.

{
    //
    // Disable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_INTEN);
}

void SysTickIntEnable

(

void

)

Enables the SysTick interrupt.

This function enables the SysTick interrupt, allowing it to be reflected to the processor.

Note

The SysTick interrupt handler is not required to clear the SysTick interrupt source because it is cleared automatically by the NVIC when the interrupt handler is called.

Returns

None.

Definition at line 174 of file systick.c.

References HWREG, NVIC_ST_CTRL, and NVIC_ST_CTRL_INTEN.

Referenced by scheduler_reschedule(), and systick_init().

{
    //
    // Enable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_INTEN;
}

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void SysTickIntRegister

(

void(*)(void)

pfnHandler

)

Registers an interrupt handler for the SysTick interrupt.

Parameters

pfnHandler

is a pointer to the function to be called when the SysTick interrupt occurs.

This function registers the handler to be called when a SysTick interrupt occurs.

See also

IntRegister() for important information about registering interrupt handlers.

Returns

None.

Definition at line 119 of file systick.c.

References FAULT_SYSTICK, HWREG, IntRegister(), NVIC_ST_CTRL, and NVIC_ST_CTRL_INTEN.

{
    //
    // Register the interrupt handler, returning an error if an error occurs.
    //
    IntRegister(FAULT_SYSTICK, pfnHandler);

    //
    // Enable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_INTEN;
}

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void SysTickIntUnregister

(

void

)

Unregisters the interrupt handler for the SysTick interrupt.

This function unregisters the handler to be called when a SysTick interrupt occurs.

See also

IntRegister() for important information about registering interrupt handlers.

Returns

None.

Definition at line 146 of file systick.c.

References FAULT_SYSTICK, HWREG, IntUnregister(), NVIC_ST_CTRL, and NVIC_ST_CTRL_INTEN.

{
    //
    // Disable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_INTEN);

    //
    // Unregister the interrupt handler.
    //
    IntUnregister(FAULT_SYSTICK);
}

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uint32_t SysTickPeriodGet

(

void

)

Gets the period of the SysTick counter.

This function returns the rate at which the SysTick counter wraps, which equates to the number of processor clocks between interrupts.

Returns

Returns the period of the SysTick counter.

Definition at line 245 of file systick.c.

References HWREG, and NVIC_ST_RELOAD.

{
    //
    // Return the period of the SysTick counter.
    //
    return(HWREG(NVIC_ST_RELOAD) + 1);
}

void SysTickPeriodSet

(

uint32_t

ui32Period

)

Sets the period of the SysTick counter.

Parameters

ui32Period

is the number of clock ticks in each period of the SysTick counter and must be between 1 and 16,777,216, inclusive.

This function sets the rate at which the SysTick counter wraps, which equates to the number of processor clocks between interrupts.

Note

Calling this function does not cause the SysTick counter to reload immediately. If an immediate reload is required, the NVIC_ST_CURRENT register must be written. Any write to this register clears the SysTick counter to 0 and causes a reload with the ui32Period supplied here on the next clock after SysTick is enabled.

Returns

None.

Definition at line 221 of file systick.c.

References ASSERT, HWREG, and NVIC_ST_RELOAD.

Referenced by scheduler_reschedule(), and systick_init().

{
    //
    // Check the arguments.
    //
    ASSERT((ui32Period > 0) && (ui32Period <= 16777216));

    //
    // Set the period of the SysTick counter.
    //
    HWREG(NVIC_ST_RELOAD) = ui32Period - 1;
}

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uint32_t SysTickValueGet

(

void

)

Gets the current value of the SysTick counter.

This function returns the current value of the SysTick counter, which is a value between the period - 1 and zero, inclusive.

Returns

Returns the current value of the SysTick counter.

Definition at line 264 of file systick.c.

References HWREG, and NVIC_ST_CURRENT.

{
    //
    // Return the current value of the SysTick counter.
    //
    return(HWREG(NVIC_ST_CURRENT));
}