AnsweredAssumed Answered

MCF5251 PLL register setting

Question asked by Brent Jenkins on Dec 17, 2013

 

What is the recommended PLL config register setting to achieve a bus frequency of 66.013MHz in the MCF5251 processor?  We previously used the MCF5249 processor and used a PLL config register setting of 0x125A3101.  This gave us a clock frequency of 132.0256MHz or a bus frequency of half that - 66.013MHz.  I've tried a value of 0x1402E045.  This results in a clock frequency that is half of what I'm looking for (I can verify this by looking at PSTCLK).  When I change the CPUDIV divisor in the PLL config register from 4 to 2 (in order to double the frequency) my debugger immediately hangs.  I can view the PSTCLK and see that it it 132MHz but the processor is not running.  I understand there are only certain values that will work.  What value in the PLL config register will work for me?  The crystal frequency is 11.2896MHz.  It is configured without a driver (using CRIN and CROUT).  Could it be that the processor is actually running but it's the debugger that's hung.  We use the P&E Micro USB Coldfire Multilink.

Outcomes