mc68hc908gr8vp Freescale Semiconductor, Inc, mc68hc908gr8vp Datasheet - Page 74

• Manufacturer Part Number: mc68hc908gr8vp
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGMC)
74
4. Select a VCO frequency multiplier, N.
5. If N is < N
6. Calculate and verify the adequacy of the VCO and bus frequencies f
7. Select the VCO’s power-of-two range multiplier E, according to this table:
8. Select a VCO linear range multiplier, L, where f
When the tolerance on the bus frequency is tight, choose f
and R = 1. If f
practical choices of f
Reduce N/R to the lowest possible R.
Then recalculate N:
max
, use P = 0. If N > N
RCLK
NOTE: Do not program E to a value of 3.
R
cannot meet this requirement, use the following equation to solve for R with
RCLK
=
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
round R
, and choose the f
19,660,800 ≤ f
9,830,400 ≤ f
N max
N max
Frequency Range
0 < f
N
N max
MAX
f
N
VCLK
L
max
=
Current N Value
VCLK
=
0
=
×
×
×
round
<
f
, choose P using this table:
<
2
4
round
round
VCLK
BUS
⎧
⎨
⎩
VCLK
N
=
<
<
N
< 8 MHz
⎛
⎜
⎝
f
------------------------- -
≤
N
N
VCLKDES
≤
(
N max
2
f
< 16 MHz
⎛
⎜
⎝
N max 2
≤
≤
RCLK
=
< 32 MHz
P
R
------------------------------------ -
⎛
⎜
⎝
⎛
⎜
⎝
N max 4
N max 8
RCLK
--------------------------
2
R
------------------------------------ -
×
(
×
f
E
f
VCLK
N R
f
×
RCLK
f
f
VCLK
×
VCLKDES
RCLK
×
NOM
f
⁄
VCLKDES
f
⎞
⎟
⎠
×
×
that gives the lowest R.
NOM
–
)
) 4 ⁄
×
×
integer
= 38.4 kHz
2
⎞
⎟
⎠
f
RCLK
P
⎞
⎟
⎠
⎞
⎟
⎠
RCLK
⎛
⎜
⎝
f
------------------------- -
VCLKDES
P
0
1
2
3
f
RCLK
to an integer divisor of f
E
0
1
2
VCLK
⎞
⎟
⎠
⎫
⎬
⎭
and f
Freescale Semiconductor
BUS
.
BUSDES
,