Wrong PWM

Posted on November 14, 2003 at 09:48

Dear all,

The PWM generator of the ST7LITE09 seems to have some problems at hight frequencies (e.g. period: 30usec). Infact by changing the duty cycle close to the ends of the period, the signal is completely wrong!!(FYI I'm using an external clock 16MHz and autoreload timer).

Thanks for your help.

Posted on November 24, 2003 at 10:56

There is a caution given in the lite0 datsheet-

Caution: At each OVF event, the DCRx value is

written in a shadow register, even if the DCR0L

value has not yet been written (in this case, the

shadow register will contain the new DCR0H value

and the old DCR0L value).

So, if you are not able to write DCR0L before OVF event, you will be getting the wrong frequency.