s908ab32ag0cfue Freescale Semiconductor, Inc, s908ab32ag0cfue Datasheet - Page 138

• Manufacturer Part Number: s908ab32ag0cfue
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGM)
9.4.2.4 Programming the PLL
Technical Data
138
NOTE:
and require fast start-up. The following conditions apply when in manual
mode:
The following procedure shows how to program the PLL.
The round function in the following equations means that the real
number should be rounded to the nearest integer number.
1. Choose the desired bus frequency, f
2. Calculate the desired VCO frequency (four times the desired bus
3. Choose a practical PLL reference frequency, f
4. Select a VCO frequency multiplier, N.
•
•
•
•
•
ACQ is a writable control bit that controls the mode of the filter.
Before turning on the PLL in manual mode, the ACQ bit must be
clear.
Before entering tracking mode (ACQ = 1), software must wait a
given time, t
Specifications), after turning on the PLL by setting PLLON in the
PLL control register (PCTL).
Software must wait a given time, t
before selecting the PLL as the clock source to CGMOUT
(BCS = 1).
The LOCK bit is disabled.
CPU interrupts from the CGM are disabled.
frequency).
Clock Generator Module (CGM)
ACQ
(see
f
N
VCLKDES
=
9.10 Acquisition/Lock Time
round
=
4 f


f
--------------------- -
×
VCLKDES
f
AL
RCLK
BUSDES
, after entering tracking mode
BUSDES


MC68HC908AB32
.
Freescale Semiconductor
RCLK
.
—
Rev. 1.1