# OS_InitTick

## Syntax

      #include <nitro/os.h>

      void OS_InitTick( void );

## Arguments

None.

## Return Values

None.

## Description

This function allocates a timer for ticks and initializes it.

Ticks are a method of using a hardware timer to generate a `u64` increment count. A tick is also the obtained value. Although the timer itself is 16 bits, in addition to the 16-bit cycle, which is one unit, there is also an internal counter. As a result it creates a 64-bit tick value. (The frequency of the system clock is `OS_SYSTEM_CLOCK` Hz, so ticks run at `OS_SYSTEM_CLOCK` / 64 Hz.)

The `OS_InitTick` function internally sets the tick value to 0. Therefore it is possible to assume that the value obtained with the `OS_GetTick` function is the time since `OS_InitTick()`.

A timer that is allocated for ticks becomes system-reserved. A user cannot use it as a timer with the `OS_StartTimer` function or similar functions. Do not call the `OS_InitTick` function if the user wants to use all of the timers.

Ticks are necessary when you use the alarm system. Call `OS_InitTick()` before calling the alarm system initialization declaration function `OS_InitAlarm`.

## See Also

`OS_GetTick, OS_GetTickLo, OS_SetTick, OS_InitAlarm
`

## Revision History

2004/02/25 Changed `systemClock` to `tick`.
2004/02/04 Initial version.

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