mc68hc908gr16 Freescale Semiconductor, Inc, mc68hc908gr16 Datasheet - Page 64

• Manufacturer Part Number: mc68hc908gr16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGM)
64
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
1. 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
, and choose the f
16 MHz ≤ f
8 MHz ≤ f
MC68HC908GR16 Data Sheet, Rev. 5.0
N max
N max
Frequency Range
0 < f
N
N max
MAX
L
f
N
VCLK
max
=
Current N Value
=
VCLK
0
=
×
×
VCLK
×
round
VCLK
round
<
f
, choose P using this table:
<
2
4
round
BUS
⎧
⎨
⎩
N
=
<
<
N
< 8 MHz
⎛
⎜
⎝
f
------------------------- -
≤
N
N
< 16 MHz
VCLKDES
≤
(
< 32 MHz
N max
2
f
⎛
⎜
⎝
N max 2
≤
≤
RCLK
=
n
P
R
------------------------------------ -
⎛
⎜
⎝
N max 4
N max 8
RCLK
⎛
⎜
⎝
R
------------------------------------ -
×
(
×
--------------------------
2
f
f
VCLK
N R
E
×
RCLK
f
f
f
VCLKDES
RCLK
VCLK
×
NOM
×
f
⁄
VCLKDES
⎞
⎟
⎠
×
×
that gives the lowest R.
f
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
(1)
VCLK
⎞
⎟
⎠
⎫
⎬
⎭
and f
Freescale Semiconductor
BUS
.
BUSDES
,