ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 28

• 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

Low-frequency
Crystal Oscillator
External RC
Oscillator
28
ATmega8(L)
Table 5. Start-up Times for the Crystal Oscillator Clock Selection
Notes:
To use a 32.768kHz watch crystal as the clock source for the device, the Low-frequency Crystal
Oscillator must be selected by setting the CKSEL Fuses to “1001”. The crystal should be con-
nected as shown in
enable internal capacitors on XTAL1 and XTAL2, thereby removing the need for external capac-
itors. The internal capacitors have a nominal value of 36pF.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Note:
For timing insensitive applications, the external RC configuration shown in
can be used. The frequency is roughly estimated by the equation f = 1/(3RC). C should be at
CKSEL0
SUT1..0
00
01
10
11
0
0
0
0
1
1
1
1
6.
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
1. These options should only be used if frequency stability at start-up is not important for the
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals
at start-up. They can also be used with crystals when not operating close to the maximum fre-
quency of the device, and if frequency stability at start-up is not important for the application
application
SUT1..0
Start-up Time from
Power-down and
00
01
10
11
00
01
10
11
Power-save
1K CK
1K CK
32K CK
Figure 11 on page
from Power-down
and Power-save
(1)
(1)
Start-up Time
258 CK
258 CK
1K CK
1K CK
1K CK
16K CK
16K CK
16K CK
(2)
(2)
(2)
(1)
(1)
Additional Delay
(V
from Reset
CC
4.1ms
65ms
65ms
27. By programming the CKOPT Fuse, the user can
= 5.0V)
Additional Delay
Reserved
(V
from Reset
CC
4.1ms
4.1ms
4.1ms
65ms
65ms
65ms
= 5.0V)
–
–
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Ceramic resonator, BOD
enabled
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
Figure 12 on page 29
2486Z–AVR–02/11