MC68HC908LB8CPE Freescale Semiconductor, MC68HC908LB8CPE Datasheet - Page 110

• 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)
10.9 HRP Programming Examples
The HRP has been designed to simplify the software required to generate typical control waveforms and
reduce the CPU load.
The following examples show how to calculate the register values needed to generate the desired output
frequencies, resolutions, deadtime, etc. The examples consider only the case of variable frequency
mode, but the calculations for variable duty cycle mode are very similar.
Example 1
This example shows how to configure the module to output a frequency of 132.073 kHz, with an HRPCLK
of 8 MHz.
If we use 32 steps, simplifying the last equation gives
If we choose STEP[4:0] = 19, the output frequency = 132.026 kHz.
If we choose STEP[4:0] = 18, the output frequency = 132.094 kHz.
So STEP[4:0] = 19 gets us closer to our desired frequency of 132.073 kHz
In this case, the switching frequency is 132.094 kHz/32 = 4.1279 kHz.
110
Period (seconds)
P 10:0
[
Therefore,
]
P 10:0
+
[
INT
-------------------------------------------- -
=
⎛
⎝
]
------------------ -
2
STEP 4:0
---------------------------- -
=
-------------------- -
132.073
SEL[2:0]
2
STEP 4:0
32
10
SEL[2:0]
60
–
[
3
=
[
STEP 4:0
---------------------------- -
MC68HC908LB8 Data Sheet, Rev. 1
$3C
]
=
⎞
⎠
]
7.57157
32
=
=
and
[
7.57157
0.5725
]
INT
-------------------------------------------- -
=
¥
10
0.5725
⎛
⎝
¥
¥
------------------ -
2
STEP 4:0
---------------------------- -
32
–
SEL[2:0]
8
2
6
32
SEL[2:0]
=
=
=
[
60.5725
P 10:0
--------------------
8
18.32
[
¥
]
10
⎞
⎠
6
=
]
=
+
=
0.5725
18 or 19
INT
-------------------------------------------- -
------------------ -
2
60
SEL[2:0]
32
⎛
⎝
+
STEP 4:0
---------------------------- -
0.5725
2
SEL[2:0]
¥
8
[
¥
10
]
⎞
⎠
6
Freescale Semiconductor
(EQ 10-16)
(EQ 10-17)
(EQ 10-18)
(EQ 10-19)
(EQ 10-20)