MC812A4CPVE8 Freescale Semiconductor, MC812A4CPVE8 Datasheet - Page 141

• Manufacturer Part Number: MC812A4CPVE8
• Description: IC MCU 16BIT EEPROM 4K 112-LQFP
• Manufacturer: Freescale Semiconductor
• Series: HC12r

Specifications of MC812A4CPVE8

• Core Processor: CPU12
• Core Size: 16-Bit
• Speed: 8MHz
• Connectivity: SCI, SPI
• Peripherals: POR, WDT
• Number Of I /o: 83
• Program Memory Size: 4KB (4K x 8)
• Program Memory Type: EEPROM
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 112-LQFP
• Processor Series: HC812A
• Core: HC12
• Data Bus Width: 16 bit
• Data Ram Size: 1 KB
• Interface Type: SCI, SPI
• Maximum Clock Frequency: 8 MHz
• Number Of Programmable I/os: 91
• Number Of Timers: 8
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8 bit, 8 Channel
• Controller Family/series: 68HC12
• No. Of I/o's: 91
• Eeprom Memory Size: 4KB
• Ram Memory Size: 1KB
• Cpu Speed: 8MHz
• No. Of Timers: 1
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

12.11 Using the Output Compare Function to Generate a Square Wave
This timer exercise is intended to utilize the output compare function to generate a square wave of
predetermined duty cycle and frequency.
The program generates a square wave, 50 percent duty cycle, on output compare 2 (OC2). The signal
will be measured by the M68HC11 on the UDLP1 board. It assumes a 8.0 MHz operating frequency for
the E clock. The control registers are initialized to disable interrupts, configure for proper pin control action
and also the TC2H register for desired compare value. The appropiate count must be calculated to
achieve the desired frequency and duty cycle. For example: for a 50 percent duty, 1 kHz signal each
period must consist of 2048 counts or 1024 counts high and 1024 counts low. In essence a $0400 is
added to generate a frequency of 1 kHz.
12.11.1 Sample Calculation to Obtain Period Counts
The sample calculation to obtain period counts is:
12.11.2 Equipment
For this exercise, use the M68HC812A4EVB emulation board.
12.11.3 Code Listing
Freescale Semiconductor
•
•
For 1000 Hz frequency:
–
–
–
For a 1 kHz, 50 percent duty cycle:
–
–
E-clock = 8 MHz
IC/OC resolution factor = 1/(E-clock/prescaler)
If the prescaler = 4, then output compare resolution is 0.5 µs
1/F = T = 1/1000 = 1 ms
F for output compare = prescaler/E clock = 2 MHz
A comment line is delimited by a semicolon. If there is no code before
comment, a semicolon (;) must be placed in the first column to avoid
assembly errors.
Square wave frequency 1000 Hz, duty cycle 50%
1 ms
Figure 12-27. Example Waveform
0.5 ms
MC68HC812A4 Data Sheet, Rev. 7
Using the Output Compare Function to Generate a Square Wave
NOTE
NUMBER OF CLOCKS = F * D
THEREFORE,
# CLOCKS = (2 MHz) * (0.5 ms) = 1024 = $0400
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