Wrong Fpwm?!

lseletron · ‎2006-07-27

Posted on July 27, 2006 at 10:46

Wrong Fpwm?!

lseletron · ‎2006-07-20

Posted on July 21, 2006 at 00:26

Hi,

I am using DVP3 emulator set for ST7DALI. I intitialize the PMW module like this:

ATCSR=0x12; // Fcount=Fosc and overflow intr enabled

ATR=0; // I want minimum Fpwm

PWMCR=0x1; // Enable PWM output #0

DCR0=4095; // Duty cycle

TRANCR=1;

The datasheet specifies that for Fosc=4MHz FpwmMax=2MHz and FpwmMin=1KHz (of course ATR must change). The problem is that I get half these values ie for FpwmMax I get 1Mhz and for FpwmMin I get 500Hz. This happens only when I specify that Fcount=Fosc. If I specify Fcount=32MHz everything is OK.

I also set DVP3 for a LITE chip and again I got half the frequencies specified in datasheet.

Thank you

zsavov

laurent239955_stm1 · ‎2006-07-27

Posted on July 27, 2006 at 10:46

Hi,

It is normal as you set Fosc to 4Mhz then Fcpu is 2MHz.

The value are given according to Fcpu. Have a look in the Clock management block diagram in the datasheet.

Best regards

Laurent