ATmega644P Automotive Atmel Corporation, ATmega644P Automotive Datasheet - Page 145
ATmega644P Automotive
Manufacturer Part Number
ATmega644P Automotive
Description
Manufacturer
Atmel Corporation
Specifications of ATmega644P Automotive
Flash (kbytes)
64 Kbytes
Pin Count
44
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
32
Ext Interrupts
32
Usb Speed
No
Usb Interface
No
Spi
3
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)
2048
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
Yes
Temp. Range (deg C)
-40 to 125
I/o Supply Class
2.7 to 5.5
Operating Voltage (vcc)
2.7 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
6
Input Capture Channels
1
Pwm Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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15.7
15.7.1
15.7.2
7674F–AVR–09/09
Modes of Operation
Normal Mode
Clear Timer on Compare Match (CTC) Mode
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is
defined by the combination of the Waveform Generation mode (WGM22:0) and Compare Output
mode (COM2x1:0) bits. The Compare Output mode bits do not affect the counting sequence,
while the Waveform Generation mode bits do. The COM2x1:0 bits control whether the PWM out-
put generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes
the COM2x1:0 bits control whether the output should be set, cleared, or toggled at a compare
match
For detailed timing information refer to
The simplest mode of operation is the Normal mode (WGM22:0 = 0). In this mode the counting
direction is always up (incrementing), and no counter clear is performed. The counter simply
overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then restarts from the bot-
tom (0x00). In normal operation the Timer/Counter Overflow Flag (TOV2) will be set in the same
timer clock cycle as the TCNT2 becomes zero. The TOV2 Flag in this case behaves like a ninth
bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt
that automatically clears the TOV2 Flag, the timer resolution can be increased by software.
There are no special cases to consider in the Normal mode, a new counter value can be written
anytime.
The Output Compare unit can be used to generate interrupts at some given time. Using the Out-
put Compare to generate waveforms in Normal mode is not recommended, since this will
occupy too much of the CPU time.
In Clear Timer on Compare or CTC mode (WGM22:0 = 2), the OCR2A Register is used to
manipulate the counter resolution. In CTC mode the counter is cleared to zero when the counter
value (TCNT2) matches the OCR2A. The OCR2A defines the top value for the counter, hence
also its resolution. This mode allows greater control of the compare match output frequency. It
also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in
(TCNT2) increases until a compare match occurs between TCNT2 and OCR2A, and then coun-
ter (TCNT2) is cleared.
Figure 15-5. CTC Mode, Timing Diagram
TCNTn
OCnx
(Toggle)
Period
(See “Compare Match Output Unit” on page
1
2
“Timer/Counter Timing Diagrams” on page
3
ATmega164P/324P/644P
143.).
Table 15-5 on page
4
145. The counter value
OCnx Interrupt Flag Set
(COMnx1:0 = 1)
149.
145
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