ST7FLiteXX: watchdog-problem with PLL-options

[wolfgang2399]

Posted on May 10, 2005 at 05:34

ST7FLiteXX: watchdog-problem with PLL-options

[wolfgang2399]

Posted on April 29, 2005 at 11:01

Thanks to glec and (indirectly) to sjo who solved the problem (last posted message at 16-02-2005) time before I got it.......

And warning to all others who use the watchdog in a ST7FLite application and think/hope it works.

As glec already found out, when the PLL is disabled and you select PLLx4 option, the watchdog won't work - with PLLx8 it works.

I was passing on to a crystal oscillator, disabled the PLL with the corresponding bit of the option-byte and left PLLx4. It took a long time to realize that the watchdog didn't work properly.

Question to glec or sjo: did you find any notice referring to this fact in an official document??

Another question: Why in Table 23 the PLLx4 option is not filled in for 3.3V-5.5V (anyhow: in my application it works)?

Regards, WoRo

[anshul]

Posted on May 09, 2005 at 06:45

Regarding your fisrt problem - the watchdog problem please can you specify which Lite device you are referring to. Thanks to also elaborate on the problem because there is no known Wtachdog problem on any Lite MCU.

Regarding, the use of PLLx4 at Vdd 3.3 - 5 V. This PLL option is not available in this reange for device Lite0 and Lite2 because it has not been designed for this range and it will not provide the 1% accuracy with the Internal RC.

[wolfgang2399]

Posted on May 10, 2005 at 05:34

Hi Ansh,

I'm using the ST7FLite29 and got exactly the same problem, which glec has already described in his message on 2004-11-11 (last posted message on 2005-02-16) for a Flite15:

With a disabled PLL and selected PLLx4 the watchdog won't work at all, with PLLx8 and also disabled PLL - :o - it works.

WoRo