RE: 4MHz crystal or 20MHz crystal??

yes. you can get the same frequencies with either crystal, however, each
requires different settings of the multiplication factor (MF) and the
pre-divider of the PLL (DIVF). These are set in the PLPRCR (register).
To get to 56 MHz, the input to the PLL must be set to 2 MHz to obtain 56
MHz system frequency.
 
Choice of crystal depends on two main trade offs:
- 4 MHz crystal has lower crystal operating current (on KAPWR power
supply)
- 20 MHz crystal has slightly better jitter performance if the MF is
kept low.

________________________________

From: [email protected] [mailto:[email protected]] On Behalf
Of huzaec
Sent: Monday, April 23, 2007 6:50 AM
To: [email protected]
Subject: [MPC500] 4MHz crystal or 20MHz crystal??



what is the difference in system clock speed if we choose 20MHz 
crystal instead of 4MHz crystal in MPC565???
or its the same thing and that we can achieve the same frequency of 
56MHz by using both the crystals??

.


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