ATmega88 Atmel Corporation, ATmega88 Datasheet - Page 153

• Manufacturer Part Number: ATmega88
• Manufacturer: Atmel Corporation

Specifications of ATmega88

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 24
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• 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): 1
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 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

18.11 Register description
18.11.1
2545T–AVR–05/11
TCCR2A – Timer/counter control register A
The clock source for Timer/Counter2 is named clk
system I/O clock clk
clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter
(RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can
then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock
source for Timer/Counter2. The Oscillator is optimized for use with a 32.768kHz crystal.
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSRASY bit in GTCCR resets the prescaler. This allows the user to operate with a
predictable prescaler.
• Bits 7:6 – COM2A1:0: Compare match output A mode
These bits control the Output Compare pin (OC2A) behavior. If one or both of the COM2A1:0
bits are set, the OC2A output overrides the normal port functionality of the I/O pin it is connected
to. However, note that the Data Direction Register (DDR) bit corresponding to the OC2A pin
must be set in order to enable the output driver.
When OC2A is connected to the pin, the function of the COM2A1:0 bits depends on the
WGM22:0 bit setting.
are set to a normal or CTC mode (non-PWM).
Table 18-2.
Table 18-3 on page 154
to fast PWM mode.
Bit
(0xB0)
Read/write
Initial value
T2S
COM2A1
/128, clk
0
0
1
1
T2S
Compare output mode, non-PWM mode.
COM2A1
R/W
/256, and clk
COM2A0
7
0
0
1
0
1
IO
Table 18-2
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
COM2A0
shows the COM2A1:0 bit functionality when the WGM21:0 bits are set
R/W
6
0
Description
Normal port operation, OC2A disconnected
Toggle OC2A on compare match
Clear OC2A on compare match
Set OC2A on compare match
T2S
/1024. Additionally, clk
shows the COM2A1:0 bit functionality when the WGM22:0 bits
COM2B1
R/W
5
0
COM2B0
R/W
4
0
T2S
. clk
R
3
0
–
T2S
T2S
as well as 0 (stop) may be selected.
is by default connected to the main
ATmega48/88/168
R
2
–
0
T2S
WGM21
/8, clk
R/W
1
0
T2S
WGM20
R/W
/32, clk
0
0
TCCR2A
T2S
/64,
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