MC68HC908MR8CFA Freescale Semiconductor, MC68HC908MR8CFA Datasheet - Page 120

• Manufacturer Part Number: MC68HC908MR8CFA
• Description: IC MCU 8K FLASH 8MHZ PWM 32-LQFP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908MR8CFA

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SCI
• Peripherals: LVD, POR, PWM
• Number Of I /o: 16
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 7x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

Clock Generator Module (CGM)
8.4.2.4 Programming the PLL
Technical Data
120
CAUTION:
NOTE:
This 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.
Exceeding the recommended maximum bus frequency or VCO
frequency can crash the MCU.
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.
5. Calculate and verify the adequacy of the VCO and bus
6. Select a VCO linear range multiplier, L.
7. Calculate and verify the adequacy of the VCO programmed
8. Verify the choice of N and L by comparing f
9. Program the PLL registers accordingly:
frequency).
frequencies f
where f
center-of-range frequency, f
f
application’s tolerance of f
possible to f
a. In the upper four bits of the PLL programming register (PPG),
b. In the lower four bits of the PLL programming register (PPG),
VCLKDES
program the binary equivalent of N.
program the binary equivalent of L.
Clock Generator Module (CGM)
NOM
. For proper operation, f
VCLK
= 4.9152 MHz
VCLK
f
.
VCLKDES
and f
f
f
VCLK
BUS
f
VRS
BUS
VCLKDES
=
= (L) f
.
=
=
VRS
(
N
f
4
VCLK
×
×
.
f
f
NOM
VCLK
RCLK
BUSDES
, and f
) 4 ⁄
BUSDES
must be within the
VRS
MC68HC908MR8 — Rev 4.1
VCLK
.
Freescale Semiconductor
must be as close as
RCLK
to f
.
VRS
and