MC68HC908LB8CPE Freescale Semiconductor, MC68HC908LB8CPE Datasheet - Page 94

• Manufacturer Part Number: MC68HC908LB8CPE
• Description: IC MCU 8K FLASH 8MHZ 20DIP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908LB8CPE

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Peripherals: LVR, POR, PWM
• Number Of I /o: 18
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 7x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Connectivity: -

High Resolution PWM (HRP)
The HRP comprises four blocks, as follows
The HRP can operate in two modes.
10.4.1 The Principle of Frequency Dithering
Frequency dithering is an averaging technique, which can increase the resolution of an output signal by
switching between two frequencies. By varying the time spent on each frequency, the average output
frequency will be a value between the two frequencies. For example, in
between 10 kHz and 20 kHz over a fixed cycle time. 30% of each cycle is spent at 20 kHz, 70% at 10 kHz.
The equivalent average frequency over time is 13 kHz.
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1. A dual frequency generator, which generates a pair of complementary PWM output signals. It
2. A dithering controller, or timebase, which sets the dithering cycle time and the percentage of time
3. Two deadtime generators, for inserting deadtime into the output signals.
4. A set of control registers
1. Variable Frequency Mode: for variation of the output frequency at a fixed 50% duty cycle
2. Variable Duty Cycle Mode: for variation of the duty cycle at a fixed frequency.
allows dithering between two adjacent frequencies or duty cycles to increase the resolution of the
output signal. After deadtime insertion, these signals are routed to the TOP and BOT output pins
spent on each of the dithering frequencies or duty cycles.
REGISTERS
CONTROL
BUSCLK
Figure 10-3. Block Diagram of High Resolution PWM (HRP)
CONTROLLER
FREQUENCY
GENERATOR
DITHERING
DUAL
MC68HC908LB8 Data Sheet, Rev. 1
DEADTIME GENERATOR
DEADTIME GENERATOR
COMPLEMENTARY OUTPUTS
WITH PROGRAMMABLE DEADTIME
HRPCLK
SHUTDOWN DETECT INPUT
FOR FAST DISABLING
Figure 10-4
OF OUTPUTS
Freescale Semiconductor
a signal switches
TOP
BOT
SHTDWN