# Development Guidelines - [Available APIs](#section158501652121514) - [How to Develop](#section783435801510) - [Development Example](#section460018317164) - [Example Description](#section127752801718) - [Sample Code](#section321653551711) - [Verification](#section4366193318167) The time management module provides APIs to implement conversion between the system running time, ticks, and seconds/milliseconds. ## Available APIs The following table describes APIs available for the OpenHarmony LiteOS-M time management. For more details about the APIs, see the API reference. **Table 1** APIs of the time management module

Category	API	Description
Time conversion	LOS_MS2Tick	Converts milliseconds into ticks.
	LOS_Tick2MS	Converts ticks into milliseconds.
	OsCpuTick2MS	Converts cycles into milliseconds. Two UINT32 values indicate the high-order and low-order 32 bits of the result value, respectively.
	OsCpuTick2US	Converts cycles into microseconds. Two UINT32 values indicate the high-order and low-order 32 bits of the result value, respectively.
Time statistics	LOS_SysClockGet	Obtains the system clock.
	LOS_TickCountGet	Obtains the number of ticks since the system starts.
	LOS_CyclePerTickGet	Obtains the number of cycles for each tick.

## How to Develop The typical development process of time management is as follows: 1. Complete board configuration and adaptation as required, and configure the system clock frequency \(**OS\_SYS\_CLOCK** in Hz and **LOSCFG\_BASE\_CORE\_TICK\_PER\_SECOND**\). The default value of **OS\_SYS\_CLOCK** varies with the hardware platform. 2. Call the clock conversion and statistics APIs. >![](../public_sys-resources/icon-note.gif) **NOTE:** >- The time management module depends on **OS\_SYS\_CLOCK** and **LOSCFG\_BASE\_CORE\_TICK\_PER\_SECOND**. >- The number of system ticks is not counted when the interrupt feature is disabled. Therefore, the number of ticks cannot be used as the accurate time. >- The configuration options are maintained in the **target\_config.h** file of the development board project. ## Development Example ### Example Description The following example describes basic time management methods, including: 1. Time conversion: converts milliseconds to ticks or converts ticks to milliseconds. 2. Time statistics: obtains the number of cycles per tick, number of ticks since system startup, and number of delayed ticks. ### Sample Code Prerequisites - The default value of **LOSCFG\_BASE\_CORE\_TICK\_PER\_SECOND** is **100**. - The system clock frequency **OS\_SYS\_CLOCK** is configured. Time conversion: ``` VOID Example_TransformTime(VOID) { UINT32 ms; UINT32 tick; tick = LOS_MS2Tick(10000); // Convert 10000 ms into ticks. dprintf("tick = %d \n", tick); ms = LOS_Tick2MS(100); // Convert 100 ticks into ms. dprintf("ms = %d \n", ms); } ``` Time statistics and delay: ``` VOID Example_GetTime(VOID) { UINT32 cyclePerTick; UINT64 tickCount; cyclePerTick = LOS_CyclePerTickGet(); if(0 != cyclePerTick) { dprintf("LOS_CyclePerTickGet = %d \n", cyclePerTick); } tickCount = LOS_TickCountGet(); if(0 != tickCount) { dprintf("LOS_TickCountGet = %d \n", (UINT32)tickCount); } LOS_TaskDelay(200); tickCount = LOS_TickCountGet(); if(0 != tickCount) { dprintf("LOS_TickCountGet after delay = %d \n", (UINT32)tickCount); } } ``` ### Verification The development is successful if the return result is as follows: Time conversion: ``` tick = 1000 ms = 1000 ``` Time statistics and delay: ``` LOS_CyclePerTickGet = 495000 LOS_TickCountGet = 1 LOS_TickCountGet after delay = 201 ```