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Why peripheral frequency doesn't tally with clock frequency and PLL?

Latest Updated:09/04/2009

Question:

For M16C/tiny series MCU, why the peripheral frequency value used doesn't tally with my clock frequency and PLL multiplication factor selection ?
Example: For M16C/26A, I selected 16MHz clock and PLL multiplying factor of 2 in main window, but the frequency displayed on bottom bar of peripheral window is 20MHz.

Answer:

When PLL is used, according to combination of user selection clock frequency and PLL multiplying factor, there is possibility that the calculated frequency falls to invalid range. When such situation happen, IO Wizard will automatically set to use the maximum PLL clock frequency.
Refer to above example : For M16C/26A, PLL clock frequency spec is 10MHz to 20MHz. When calculated frequency is (16MHz x 2) which is 32MHz (invalid), IO Wizard will automatically set to use 20MHz.
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