MC68HC908GR16 Datasheet, PDF (65/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Clock Generator Module (CGM)
Functional Description
4. Select a VCO frequency multiplier, N.
N
=
r
ou
nd



R------×_{-----ff--VR----CC---L-L--K-K---D----E---S--}
Reduce N/R to the lowest possible R.
5. If N is < N_max, use P = 0. If N > N_max, choose P using this table:
Current N Value
P
0 < N ≤ Nmax
0
Nmax < N ≤ Nmax × 2
1
Nmax × 2 < N ≤ Nmax × 4
2
Nmax × 4 < N ≤ Nmax × 8
3
Then recalculate N:
N
=
r
ou
n

d

-R----f-^×-_R---_C-f--^V-_L---^CK---^L--_×-^K----2^D---_P-^E---^S--_{}
6. Calculate and verify the adequacy of the VCO and bus frequencies f_VCLK
and f_BUS.
f_VCLK = (2^P × N ⁄ R) × f_RCLK
f_BUS = (f_VCLK) ⁄ 4
7. Select the VCO’s power-of-two range multiplier E, according to this table:
Frequency Range
E⁽¹⁾
0 < f_VCLK < 8 MHz
0
8 MHz ≤ f_VCLK < 16 MHz
1
16 MHz ≤ f_VCLK < 32 MHz
2
1. Do not program E to a value of 3.
8. Select a VCO linear range multiplier, L, where f_NOM = 38.4 kHz
L
=
r
ou
n
dn

2----^E--f--V-×^---C--f-_NL^----KO----_M^{---}
MC68HC908GR16 — Rev. 1.0
MOTOROLA
Clock Generator Module (CGM)
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
65