MC68HC908LB8CPE Freescale Semiconductor, MC68HC908LB8CPE Datasheet - Page 100

• 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 formula for calculating the output duty cycle in variable duty cycle mode is:
where 2
In Variable Duty Cycle Mode, the individual periods and duty cycles are given by:
10.4.7 Dithering Controller
The dithering controller consists of a 5-bit counter with programmable modulus. The counter contents are
compared with a scaled version of the STEP[4:0] bits.
The modulus value (i.e., the total number of steps) and the STEP[4:0] scaling factor are set by the SEL
bits in the HRP configuration register.
STEP[4:0] bits is linked to the modulus value. For example, if a modulus of 32 is chosen, STEP[4:0] is not
scaled (32 steps of dithering are available). If a modulus of 16 is chosen, STEP[4:0] is divided by 2, so
that only 16 steps of dithering are available.
For example, if you decide to have 16 steps (SEL = 1) instead of the maximum of 32, and you set
STEP[4:0] equal to 23, then the scaled value of STEP will be 11 (i.e., the integer part of 23 divided by 2).
If you decide to have 4 steps instead of 32, the scaled value of 23 would be 2 (the integer part of 23 divided
by 8).
100
SEL[2:0]
is the STEP[4:0] scaling factor.
SEL
0
1
2
3
4
5
6
7
Output Duty Cycle
Table 10-3. Number of Steps and Step Scaling
DUTY2
PERIOD2
Number of Steps
PERIOD1
=
MC68HC908LB8 Data Sheet, Rev. 1
Reserved
Reserved
DUTY1
Table 10-3
DUTY1
32
16
=
=
8
4
2
0
DC 10:0
-------------------------
PERIOD1
HRPCLK
=
[
+
=
DC[10:0]
1
----------------------- -
HRPCLK
lists the available options. Note that the scaling of the
P[10:0]
=
]
+
DC[10:0]
=
------------------------------------------------- -
------------------ -
2
INT
SEL[2:0]
----------------------- -
HRPCLK
P[10:0]
32
⎛
⎝
STEP 4:0
---------------------------- -
Divide STEP[4:0] by...
2
+
¥
SEL[2:0]
1
HRPCLK
[
Reserved
Reserved
]
⎞
⎠
16
32
1
2
4
8
Freescale Semiconductor
(EQ 10-10)
(EQ 10-6)
(EQ 10-7)
(EQ 10-8)
(EQ 10-9)