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MC9S12XEP100, problem with TIM that seems to freeze sometimes

Question asked by Alessandro Audero on Apr 13, 2016
Latest reply on Apr 14, 2016 by Radek Sestak

Dear All,

I've implemented a firmware that is running well but sometimes I have an issue.

I've implemented a sleep routine like this:


void sleep_us(uint us) {   uint target;   uchar overflow;   uint now;    TIM_TFLG2_TOF = 1;   target = TIM_TCNT + us;   if (TIM_TCNT > target) {   while(TIM_TFLG2_TOF == 0);   TIM_TFLG2_TOF = 1;   }   while(TIM_TCNT < target); }


This routine is used to sleep a specified amouth of microseconds.

It is then used to implement the sleep_ms routine that is like this:


void sleep_ms(uint ms) {   uint i;   for (i = 0; i < ms; i++) sleep_us(1000); }


Everything seems to go just fine, but sometimes the sleep_ms sleeps for more time than required. For example, even if I require a sleep of 1000 ms it could happen that the sleep_ms blocks for some seconds.

While calling the sleep_us and sleep_ms there are two PIT active along with their interrupt service routine, but I don't think that they could justify the so-long sleep interval.


The timer init configuration is set using a prescaler in order to have a 1us period.


void timer_init() {      TIM_TSCR1_PRNT = 1;       TIM_PTPSR = 0x2f;       TIM_OCPD = 0xff;           TIM_TSCR1_TEN = 1;      }


I cannot figure out why the sleep should wait more time than expected. Can someone give me some hints on how to solve this problem?


Thanks in advance,











PTPSR = tim_prescaler;

TIM_TSCR1_TEN = 0; TIM_OCPD = 0xff; // scollego tutti dalle uscite. TIM_TSCR1_TEN = 1;