mc68hc908sr12 Freescale Semiconductor, Inc, mc68hc908sr12 Datasheet - Page 121

• Manufacturer Part Number: mc68hc908sr12
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

MC68HC908SR12•MC68HC08SR12 — Rev. 5.0
Freescale Semiconductor
3. Calculate N:
4. Calculate and verify the adequacy of the VCO and bus
The relationship between the VCO frequency, f
reference frequency, f
where N is the integer range multiplier, between 1 and 4095.
In cases where desired bus frequency has some tolerance,
choose f
requirements (such as modules which are clocked by CGMXCLK),
cost requirements, or ideally, as high as the specified range
allows. See
reference divider, R = 1.
When the tolerance on the bus frequency is tight, choose f
an integer divisor of f
requirement, use the following equation to solve for R with
practical choices of f
lowest R.
frequencies f
Clock Generator Module (CGM)
R
=
RCLK
round R
Section 24. Electrical
VCLK
to a value determined either by other module
N
MAX
and f
=
RCLK
BUSDES
×
round
f
f
RCLK
⎧
⎨
⎩
VCLK
VCLK
f
BUS
⎛
⎜
⎝
BUS
f
------------------------- -
VCLKDES
, and choose the f
f
⎛
⎜
⎝
RCLK
, is
.
R
------------------------------------ -
=
=
=
, and R = 1. If f
f
×
RCLK
2
----------- f
2
----------- f
---------- -
2
f
f
VCLK
P
P
R
R
P
VCLKDES
N
N
×
⎞
⎟
⎠
(
(
–
×
4
RCLK
RCLK
Specifications. Choose the
integer
2
P
Clock Generator Module (CGM)
⎞
⎟
⎠
)
)
⎛
⎜
⎝
RCLK
f
------------------------- -
RCLK
VCLKDES
f
RCLK
Functional Description
VCLK
cannot meet this
that gives the
⎞
⎟
⎠
, and the
⎫
⎬
⎭
Data Sheet
RCLK
121
to