Freescale Semiconductor HCS08 Series, Reference Manual

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Multi-Purpose Clock Generator (S08MCGV1)
MC9S08JS16 MCU Series Reference Manual, Rev. 4
140 Freescale Semiconductor
Figure 9-11. Flowchart of BLPI to FEE Mode Transition using a 4 MHz crystal
9.5.2.4 Example # 4: Moving from FEI to PEE Mode: External Crystal = 8 MHz,
Bus Frequency = 8 MHz
In this example, the MCG will move through the proper operational modes from FEI to PEE mode until
the 8 MHz crystal reference frequency is set to achieve a bus frequency of 8 MHz.
This example is similar to example number one except that in this case the frequency of the external crystal
is 8 MHz instead of 4 MHz. Special consideration must be taken with this case since there is a period of
time along the way from FEI mode to PEE mode where the FLL operates based on a reference clock with
a frequency that is greater than the maximum allowed for the FLL. This occurs because with an 8 MHz
MCGC2 = 0x36
CHECK
OSCINIT = 1 ?
MCGC1 = 0x38
CHECK
IREFST = 0?
CHECK
CLKST = %00?
CONTINUE
IN FEE MODE
START
I
N BLPI MODE
YES
YES
NO
NO
NO
MCGC2 = 0x00
OPTIONAL:
CHECK LOCK
= 1?
YES
NO
YES
OPTIONAL:
CHECK LOCK
= 1?
YES
NO