systick延时时间不准

kksxf · 发表于 2014-12-1 13:38:26

小弟尝试自己修改例程中的systick延时程序发现修改完之后延时时间明显不准了（变长）现求助各位大大
下面是例程中的程序

[mw_shl_code=c,true] u32 temp; SysTick->LOAD=(u32)time*Delaycnt_1ms; SysTick->VAL =0x00; SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk ; do { temp=SysTick->CTRL; } while(temp&0x01&&!(temp&(1<<16))); SysTick->CTRL&=~SysTick_CTRL_ENABLE_Msk; SysTick->VAL =0X00; [/mw_shl_code]

以下是我修改的程序

[mw_shl_code=c,true] SysTick->LOAD = time*Delaycnt_1ms - 1; SysTick->VAL = 0; SysTick->CTRL |= SysTick_CTRL_ENABLE_Msk; while ( ( ( SysTick->CTRL&0x01 ) !=0 ) && ( SysTick->CTRL&(1<<16) ) == 0 ) ; SysTick->CTRL &=~ SysTick_CTRL_ENABLE_Msk; SysTick->VAL = 0;[/mw_shl_code]