MCF52259 crystal & PLL

Ferberber — Wed, 20 Jul 2011 14:15:03 GMT

Hello,

I have made a board onthe basis of the M52259DEMO.

The MCF52259 operates at 80Mhz with a 48MHz crystal, the input is divided by 6 and the PLL multiplied by 10.

I connected the UART to my PC and everything is working fine.

I have read the MCF52259 Chip Errata and to be sure that my board works at all temperatures I decided to use a 25MHz crystal.

Now,

the MCF52259 operates at 80Mhz with a 25MHz crystal, the input is divided by 5 and the PLL multiplied by 16.

When connecting the UART to my PC the communication is not working.

I tried with a 24MHz crystal:

The MCF52259 operates at 80Mhz with a 24MHz crystal, the input is divided by 3 and the PLL multiplied by 10.

When connecting the UART to my PC the communication is working well again.

Something must be wrong, this looks like if the PLL 16x is not correct.

Some one have an idea?

Thanks

Re: MCF52259 crystal & PLL

mjbcswitzerland — Wed, 20 Jul 2011 17:43:13 GMT

Interesting - the PLL multiplication values 4,6,8,10,12,14,16 or 18 should be legal values.

Did you measure the baud rate that the UART was sending at to get an idea of the deviation???

Is it possible that the 25MHz crystal was oscillating at a different frequency due to incorrect loading?

Regards

Mark