topic Re: ICG won't lock in 8-bit Microcontrollers

ICG won't lock

Tacky — Fri, 12 Feb 2010 06:31:41 GMT

Hello all,

I am using a GB60 MCU and having troubles having my internal clock generator lock. I have ICG2 = 0x32 and IGC1 = 0x5C (high range, FEE).

If I set my prescale N factor to anything other than 000 the clock doesn't lock. the ERCS bit indicates the clock is stable. I need to take a 10MHz clock external clock to 12.5MHz.

while ((ICGS1_LOCK == 0) || (ICGS1_ERCS == 0))
{
__RESET_WATCHDOG();
}

Thanks for any suggestions!

Re: ICG won't lock

bigmac — Fri, 12 Feb 2010 22:42:36 GMT

Hello,

For FEE mode of the ICG, the datasheet specifies a maximum allowable external input frequency of 10 MHz. Any attempt to exceed this frequency will go beyond the upper limit of the DCO range (40 MHz), with minimum MFD setting of 4.

The use of the maximum specified external frequency of 16 MHz is applicable only to FBE mode.

Regards,

Mac

Re: ICG won't lock

Tacky — Sat, 13 Feb 2010 04:55:15 GMT

Hi Mac,

Thanks for the reply. I guess I was reading the statement in the datasheet "The maximum external clock frequency is limited to 10MHz in FEE mode to prevent over-clocking of the DCO." incorrectly.. now I am not sure how I misinterpeted this statement *facepalm*.

Changing to FBE mode and trying it out again...

Thanks again!