MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 106

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Clock Generator Module (CGM)
Advance Information
106
NOTE:
Exceeding the recommended maximum bus frequency or VCO
frequency can crash the MCU.
For proper operation,
5. Calculate the bus frequency, f
6. Using the value 4.9152 MHz for f
7. Calculate the VCO center-of-range frequency, f
8. Program the PLL registers accordingly:
If the calculated f
application, select another f
range multiplier, L. The linear range multiplier controls the
frequency range of the PLL.
center-of-range frequency is the midpoint between the minimum
and maximum frequencies attainable by the PLL.
a. In the upper four bits of the PLL programming register (PPG),
b. In the lower four bits of the PLL programming register (PPG),
program the binary equivalent of N.
program the binary equivalent of L.
Clock Generator Module (CGM)
Example: f
Example:
Example:
BUS
VRS
L
f
is not within the tolerance limits of your
VRS
= 7
f
f
=
BUS
VRS
f
BUS
L
round
–
=
=
= L
f
4.9152 MHz = 34.4 MHz
BUSDES
VCLK
------------------------------- -
4.9152 MHz
=
32 MHz
------------------- -
BUS
32 MHz
f
----------- -
VCLK
4
4
f
------------ -
f
, and compare f
NOM
f
NOM
VCLK
NOM
or another f
f
-------------- -
NOM
2
, calculate the VCO linear
=
MC68HC708AS48
8 MHz
=
7
RCLK
VRS
BUS
.
. The
with f
MOTOROLA
—
BUSDES
Rev. 4.0
.