mc68hc908gr8b Freescale Semiconductor, Inc, mc68hc908gr8b Datasheet - Page 58

• Manufacturer Part Number: mc68hc908gr8b
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGM)
58
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
9. Calculate and verify the adequacy of the VCO programmed center-of-range frequency, f
Then recalculate N:
center-of-range frequency is the midpoint between the minimum and maximum frequencies
attainable by the PLL.
For proper operation,
max
, use P = 0. If N > N
NOTE: Do not program E to a value of 3.
16MHz
8MHz
MC68HC908GR8B Data Sheet, Rev. 3.0
N max
N max
Frequency Range
0 < f
N
N max
f
N
L
VCLK
max
=
Current N Value
f
VCLK
VRS
=
0
=
f
f
VCLK
f
round
VRS
VCLK
<
f
, choose P using this table:
<
2
4
round
round
BUS
N
<
<
N
–
< 8MHz
=
N
N
< 16MHz
f
< 32MHz
=
VCLK
N max
2
N max 2
=
R
------------------------------------ -
P
N max 4
N max 8
L
--------------------------
2
R
------------------------------------ -
f
E
f
VCLK
N R
f
RCLK
f
f
VCLK
VCLKDES
RCLK
2
NOM
f
VCLKDES
f
E
f
--------------------------
NOM
NOM
f
NOM
= 38.4 kHz
2
f
4
2
RCLK
P
2
E
P
0
1
2
3
E
0
1
2
VCLK
and f
Freescale Semiconductor
BUS
.
VRS
. The