MC9S08JM16CGTE FREESCALE [Freescale Semiconductor, Inc], MC9S08JM16CGTE Datasheet - Page 201

• Manufacturer Part Number: MC9S08JM16CGTE
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

12.5.2.3
In this example, the MCG will move through the proper operational modes from BLPI mode at a 16 kHz
bus frequency running off of the internal reference clock (see previous example) to FEE mode using a 4
MHz crystal configured for a 16 MHz bus frequency. First, the code sequence will be described. Then a
flowchart will be included which illustrates the sequence.
Freescale Semiconductor
1. First, BLPI must transition to FBI mode.
2. Next, FBI will transition to FEE mode.
a) MCGC2 = 0x00 (%00000000)
b) Optionally, loop until LOCK (bit 6) in the MCGSC is set, indicating that the FLL has acquired
a) MCGC2 = 0x36 (%00110110)
b) Loop until OSCINIT (bit 1) in MCGSC is 1, indicating the crystal selected by the EREFS bit
c) MCGC1 = 0x38 (%00111000)
d) Loop until IREFST (bit 4) in MCGSC is 0, indicating the external reference clock is the current
e) Optionally, loop until LOCK (bit 6) in the MCGSC is set, indicating that the FLL has
f) Loop until CLKST (bits 3 and 2) in MCGSC are %00, indicating that the output of the FLL is
– LP (bit 3) in MCGSC is 0
lock. Although the FLL is bypassed in FBI mode, it is still enabled and running.
– RANGE (bit 5) set to 1 because the frequency of 4 MHz is within the high frequency range
– HGO (bit 4) set to 1 to configure external oscillator for high gain operation
– EREFS (bit 2) set to 1, because a crystal is being used
– ERCLKEN (bit 1) set to 1 to ensure the external reference clock is active
has been initialized.
– CLKS (bits 7 and 6) set to %00 in order to select the output of the FLL as system clock
– RDIV (bits 5-3) set to %111, or divide-by-128 because 4 MHz / 128 = 31.25 kHz which is
– IREFS (bit 1) cleared to 0, selecting the external reference clock
source for the reference clock
reacquired lock.
selected to feed MCGOUT
Example #3: Moving from BLPI to FEE Mode: External Crystal = 4 MHz,
Bus Frequency = 16 MHz
source
in the 31.25 kHz to 39.0625 kHz range required by the FLL
MC9S08JM16 Series Data Sheet, Rev. 2
Multi-Purpose Clock Generator (S08MCGV1)
201