mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 66

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGM)
66
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
=
round R
19,660,800 ≤ f
9,830,400 ≤ f
, and choose the f
N max
N max
MC68HC908GP32 Data Sheet, Rev. 10
0 < f
N max
Frequency Range
N
MAX
f
N
VCLK
L
VCLK
max
=
Current N Value
0
×
×
=
=
<
VCLK
×
round
VCLK
<
2
4
f
, choose P using this table:
< 9,830,400
round
round
N
BUS
⎧
⎨
⎩
<
<
N
=
⎛
⎜
⎝
≤
f
------------------------- -
N
N
< 19,660,800
VCLKDES
≤
(
< 39,321,600
N max
2
f
⎛
⎜
⎝
N max
≤
≤
RCLK
=
P
R f
------------------------------------ -
⎛
⎜
⎝
⎛
⎜
⎝
RCLK
N max
N max
--------------------------
2
R f
------------------------------------ -
×
(
×
f
f
E
VCLK
N R
f
×
RCLK
f
VCLK
×
VCLKDES
RCLK
NOM
⁄
VCLKDES
f
×
⎞
⎟
⎠
that gives the lowest R.
NOM
2
×
×
–
) f
) 4 ⁄
×
×
integer
4
8
= 38.4 kHz
⎞
⎟
⎠
2
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
,