HCS08 datasheet(206/374 Pages) NXP

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Multi-Purpose Clock Generator (S08MCGV1)

MC9S08JM60 Series Data Sheet, Rev. 5

206

Freescale Semiconductor

c) MCGC1 = 0x98 (%10011000)

– RDIV (bits 5-3) set to %011, or divide-by-8 because 8 MHz / 8= 1 MHz which is in the 1

MHz to 2 MHz range required by the PLL. In BLPE mode, the configuration of the RDIV

does not matter because both the FLL and PLL are disabled. Changing them only sets up the

the dividers for PLL usage in PBE mode

d) MCGC3 = 0x44 (%01000100)

– PLLS (bit 6) set to 1, selects the PLL. In BLPE mode, changing this bit only prepares the

MCG for PLL usage in PBE mode

– VDIV (bits 3-0) set to %0100, or multiply-by-16 because 1 MHz reference * 16 = 16 MHz.

In BLPE mode, the configuration of the VDIV bits does not matter because the PLL is

disabled. Changing them only sets up the multiply value for PLL usage in PBE mode

e) Loop until PLLST (bit 5) in MCGSC is set, indicating that the current source for the PLLS

clock is the PLL

3. Then, BLPE mode transitions into PBE mode:

a) Clear LP (bit 3) in MCGC2 to 0 here to switch to PBE mode

b) Then loop until LOCK (bit 6) in MCGSC is set, indicating that the PLL has acquired lock

4. Last, PBE mode transitions into PEE mode:

a) MCGC1 = 0x18 (%00011000)

– CLKS (bits7 and 6) in MCGSC1 set to %00 in order to select the output of the PLL as the

system clock source

– Loop until CLKST (bits 3 and 2) in MCGSC are %11, indicating that the PLL output is

selected to feed MCGOUT in the current clock mode

b) Now, With an RDIV of divide-by-8, a BDIV of divide-by-1, and a VDIV of multiply-by-16,

MCGOUT = [(8 MHz / 8) * 16] / 1 = 16 MHz, and the bus frequency is MCGOUT / 2, or 8 MHz

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