MTIM and related MPRSR???

rk_web04 · ‎2006-01-31

Posted on February 01, 2006 at 07:29

rk_web04 · ‎2011-05-17

Posted on May 17, 2011 at 10:19

Hi.

I have some problems in understanding by control the MPRSR ratio bits.

I found also the thread

http://mcu.st.com/mcu/modules.php?mop=modload&name=Splatt_Forums&file=viewtopic&topic=2696&forum=13

But it is not clear enough for me.

So, where exactly occur the step frequency and why is the minimum value for MTIM is 55h?

I try to drive a BLDC motor with the ST7FMC so lets check a example:

F_Periph = 4 MHz and the MPRSR Reg is loaded by 8h and the uC works in switched mode.

So, that means the MTIM works at a clock of 7,8125kHz. Now it takes 19.2ms for next C event then MCOMP comprised 150. MTIM timer is reset and 'ratio' bits will be kept at 8h.

Is this right?

Maybe it is not a smart question but it is a new field for me.

Thanks for help,

By RoB.

gaetano · ‎2011-05-17

Posted on May 17, 2011 at 10:19

Hi,

the management of ratio value for MTIM timer depends on the mode the MCU is configured: Switched or Auto-switched. The mechanism can be easily understood just before reading carefully the

http://www.st.com/stonline/books/pdf/docs/9721.pdf

at pages 168->173.

In this way, I believe that all your questions can be completely answered. If not, please, let me know further at this location.

Best regards,

Tanio