ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 120

• Manufacturer Part Number: ATmega8
• Manufacturer: Atmel Corporation

Specifications of ATmega8

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 2
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• 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: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 1
• Pwm Channels: 3
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Timer/Counter
Prescaler
Special Function IO
Register – SFIOR
120
ATmega8(L)
Figure 56. Prescaler for Timer/Counter2
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 B. 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. Apply-
ing an external clock source to TOSC1 is not recommended.
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSR2 bit in SFIOR resets the prescaler. This allows the user to operate with a pre-
dictable prescaler.
• Bit 1 – PSR2: Prescaler Reset Timer/Counter2
When this bit is written to one, the Timer/Counter2 prescaler will be reset. The bit will be cleared
by hardware after the operation is performed. Writing a zero to this bit will have no effect. This bit
will always be read as zero if Timer/Counter2 is clocked by the internal CPU clock. If this bit is
written when Timer/Counter2 is operating in Asynchronous mode, the bit will remain one until
the prescaler has been reset.
Bit
Read/Write
Initial Value
T2S
/128, clk
TOSC1
clk
PSR2
CS20
CS21
CS22
T2S
R
AS2
7
–
0
I/O
/256, and clk
I/O
R
6
–
0
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
T2S
clk
R
5
–
0
/1024. Additionally, clk
T2S
R
TIMER/COUNTER2 CLOCK SOURCE
4
–
0
Clear
0
ACME
R/W
T2S
3
0
10-BIT T/C PRESCALER
. clk
clk
T2S
T2S
T2
PUD
R/W
2
0
as well as 0 (stop) may be selected.
is by default connected to the main
PSR2
R/W
1
0
T2S
/8, clk
PSR10
R/W
0
0
T2S
/32, clk
SFIOR
2486Z–AVR–02/11
T2S
/64,