MC68HC08AS32 Datasheet, PDF (102/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Clock Generator Module (CGM)
5. Calculate the bus frequency, f_BUS, and compare f_BUS with f_BUSDES.
If the calculated f_BUS is not within the tolerance limits of your
application, select another f_BUSDES or another f_RCLK.
f_BUS = ^f---V--4^C---^L--^K-
Example: f_BUS = ^{3----2-----M4-----H----z--} = 8 MHz
6. Using the value 4.9152 MHz for f_NOM, calculate the VCO linear
range multiplier, L. The linear range multiplier controls the
frequency range of the PLL.
L
=
ro
un
d


f-f-_{V-N--C-O---L-M-K-}
Example: L = _{4----.-9-3---1-2--5---M2-----HM----z-H-----z-} = 7
7. Calculate the VCO center-of-range frequency, f_VRS. The
center-of-range frequency is the midpoint between the minimum
and maximum frequencies attainable by the PLL.
f_VRS = L × f_NOM
Example: f_VRS = 7 × 4.9152 MHz = 34.4 MHz
NOTE: Exceeding the recommended maximum bus frequency or VCO
frequency can crash the MCU.
For proper operation,
f_VRS – f_VCLK
≤
f _NOM
------₂--------
Advance Information
102
Clock Generator Module (CGM)
MC68HC08AS32 — Rev. 3.0
MOTOROLA