ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 157

• 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

17.8
8151H–AVR–02/11
Timer/Counter Timing Diagrams
match between OCR2 and TCNT2 when the counter increments, and setting (or clearing) the
OC2 Register at compare match between OCR2 and TCNT2 when the counter decrements. The
PWM frequency for the output when using phase correct PWM can be calculated by the follow-
ing equation:
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR2 Register represent special cases when generating a PWM
waveform output in the phase correct PWM mode. If the OCR2 is set equal to BOTTOM, the out-
put will be continuously low and if set equal to MAX the output will be continuously high for non-
inverted PWM mode. For inverted PWM the output will have the opposite logic values.
At the very start of Period 2 in
there is no Compare Match. The point of this transition is to guarantee symmetry around BOT-
TOM. There are two cases that give a transition without a Compare Match:
The Timer/Counter is a synchronous design and the timer clock (clk
clock enable signal in the following figures. The figures include information on when interrupt
flags are set.
shows the count sequence close to the MAX value in all modes other than phase correct PWM
mode.
Figure 17-8. Timer/Counter Timing Diagram, no Prescaling
Figure 17-9
• OCR2A changes its value from MAX, like in
• The timer starts counting from a value higher than the one in OCR2A, and for that reason
OCn pin value is the same as the result of a down-counting Compare Match. To ensure
symmetry around BOTTOM the OCn value at MAX must correspond to the result of an up-
counting Compare Match.
misses the Compare Match and hence the OCn change that would have happened on the
way up.
TCNTn
(clk
TOVn
clk
clk
I/O
I/O
Tn
/1)
shows the same timing data, but with the prescaler enabled.
Figure 17-8
MAX - 1
contains timing data for basic Timer/Counter operation. The figure
Figure 17-7
f
OCnPCPWM
MAX
OCn has a transition from high to low even though
Figure
=
----------------- -
N 510
f
clk_I/O
⋅
17-7. When the OCR2A value is MAX the
BOTTOM
T2
ATmega128A
) is therefore shown as a
BOTTOM + 1
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