ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 155

• Manufacturer Part Number: ATmega128A
• Manufacturer: Atmel Corporation

Specifications of ATmega128A

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 8
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 8
• Input Capture Channels: 2
• Pwm Channels: 7
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

8151H–AVR–02/11
togram for illustrating the single-slope operation. The diagram includes non-inverted and
inverted PWM outputs. The small horizontal line marks on the TCNT2 slopes represent compare
matches between OCR2 and TCNT2.
Figure 17-6. Fast PWM Mode, Timing Diagram
The Timer/Counter overflow flag (TOV2) is set each time the counter reaches Max If the inter-
rupt is enabled, the interrupt handler routine can be used for updating the compare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC2 pin. Set-
ting the COM21:0 bits to 2 will produce a non-inverted PWM and an inverted PWM output can
be generated by setting the COM21:0 to 3 (see
will only be visible on the port pin if the data direction for the port pin is set as output. The PWM
waveform is generated by setting (or clearing) the OC2 Register at the compare match between
OCR2 and TCNT2, and clearing (or setting) the OC2 Register at the timer clock cycle the coun-
ter is cleared (changes from MAX to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR2 Register represents special cases when generating a PWM
waveform output in the fast PWM mode. If the OCR2 is set equal to BOTTOM, the output will be
a narrow spike for each MAX+1 timer clock cycle. Setting the OCR2 equal to MAX will result in a
constantly high or low output (depending on the polarity of the output set by the COM21:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by set-
ting OC2 to toggle its logical level on each compare match (COM21:0 = 1). The waveform
generated will have a maximum frequency of f
ture is similar to the OC2 toggle in CTC mode, except the double buffer feature of the output
compare unit is enabled in the fast PWM mode.
TCNTn
OCn
OCn
Period
1
2
3
f
OCnPWM
4
OC2
Table 17-4 on page
=
= f
----------------- -
N 256
f
clk_I/O
5
clk_I/O
⋅
/2 when OCR2 is set to zero. This fea-
6
160). The actual OC2 value
7
ATmega128A
OCRn Interrupt Flag Set
OCRn Update
and
TOVn Interrupt Flag Set
(COMn1:0 = 2)
(COMn1:0 = 3)
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