XgNutArchArmZeroOsTimer

Defines
#define	NUT_TICK_FREQ   1000UL
	System timer interrupt frequency.
Functions
void	NutRegisterTimer (void(*handler)(void *))
	Initialize system timer.
uint32_t	NutArchClockGet (int idx)
	Return the specified clock frequency.
uint32_t	NutGetTickClock (void)
	Return the number of system ticks per second.
uint32_t	NutTimerMillisToTicks (uint32_t ms)
	Calculate system ticks for a given number of milliseconds.

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Define Documentation

#define NUT_TICK_FREQ   1000UL

System timer interrupt frequency.

Specifies the number of interrupts per second, typically 1000. In order to reduce overhead, you may choose lower values. Note, that Nut/OS API timer values are given in milliseconds. Thus, lower values will reduce the available resolution, while larger values may not provide any benefit.

Referenced by NutGetTickClock().

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Function Documentation

void NutRegisterTimer

(

void(*)(void *)

handler

)

Initialize system timer.

Applications must not call this function.

It is automatically called by Nut/OS during initialization to register the system timer interrupt handler. It is an essential part of the hardware dependant code and must be available for any platform that is running Nut/OS.

The number of system timer interrupts is define by NUT_TICK_FREQ.

Timer interrupts are enabled when this function returns.

Parameters:

handler

This routine should be called each time, when a system timer interrupt occurs.

uint32_t NutArchClockGet

(

int

idx

)

Return the specified clock frequency.

Return the CPU clock in Hertz.

Applications must not call this function, but use NutClockGet() instead.

Simple implementations may not provide this function, in which case NUT_CPU_FREQ must define the CPU frequency in Hertz. This can be done in the Configurator.

Parameters:

idx

This zero based index specifies the clock to retrieve. The number of available hardware clocks depends on the target harware and is specified by NUT_HWCLK_MAX + 1. Typically NUT_HWCLK_CPU is used to retrieve the current CPU clock. Additional indices may be available to retrieve one or more peripheral clocks or a special slow clock.

Returns:

Clock frequency in Hertz.

uint32_t NutGetTickClock

(

void

)

Return the number of system ticks per second.

This routine is used by Nut/OS to convert tick counts into milliseconds.

Applications typically do not deal with system ticks. Instead, they use milliseconds to specify timeouts or call NutGetMillis() and NutGetSeconds() to retrieve an elapsed time.

Returns:

System tick frequency in Hertz, typically the value of NUT_TICK_FREQ.

References NUT_TICK_FREQ.

uint32_t NutTimerMillisToTicks

(

uint32_t

ms

)

Calculate system ticks for a given number of milliseconds.

This routine is used by Nut/OS to retrieve the number of system ticks for a given timeout.

Parameters:

ms	Number of milliseconds.

Returns:

Number of system ticks. The resolution is limited to the granularity of the system timer.

References NutGetTickClock().

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