Problem with ST72F521 internal RC oscillator

[doudou140]

Posted on May 01, 2005 at 19:32

Problem with ST72F521 internal RC oscillator

[doudou140]

Posted on April 29, 2005 at 07:33

Hello,

I am using the internal RC ocsillator as the main clock of the ST7 and the frequency is supposed to be around 3MHZ.

However, i measured the ST7's frenquency at 300HZ!!!!

To mesure this frequency, I used the INdart usb card to flash the ST7 and i wrote a progam wich did a simple loop of 3600 cycles . I set a bit defore the loop, i reset it at the end of the loop and I check it with the oscilloscope.

I though that a simple reset of the ST7 would set the frequency correctly... (I connected both output OSC1 and OSC2 to the ground as it is written in the datasheet....)

How can I do to set the frequency at 3MHZ?

thanks a lot for helping me,

sincerely

[doudou140]

Posted on April 30, 2005 at 07:05

I solve the problem!!!

If you are using breakpoint to debbug your program, the soft (for inDartUSB card) write a big additionnal program in the component so after the component goes really slow (300HZ instead of 1,5MHZ). Do not used breakpoint to debug it.

Now it is working but i still do not understand why the difference is so big.

Thanks I hope it would help some of you.

[ldefend2]

Posted on May 01, 2005 at 19:32

As you can find on SofTec Microsystems FAQ page:

This happens when your target device doesn't feature the on-chip debug module. In this case, step commands are not executed in real time, for a series of reasons which are explained in detail in the user's manual addendum.