ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 40

• 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

External Reset
Brown-out Detection
40
ATmega8(L)
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the
minimum pulse width (see
running. Shorter pulses are not guaranteed to generate a reset. When the applied signal
reaches the Reset Threshold Voltage – V
MCU after the time-out period t
Figure 17. External Reset During Operation
ATmega8 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
operation by comparing it to a fixed trigger level. The trigger level for the BOD can be selected
by the fuse BODLEVEL to be 2.7V (BODLEVEL unprogrammed), or 4.0V (BODLEVEL pro-
grammed). The trigger level has a hysteresis to ensure spike free Brown-out Detection. The
hysteresis on the detection level should be interpreted as
V
The BOD circuit can be enabled/disabled by the fuse BODEN. When the BOD is enabled
(BODEN programmed), and V
18), the Brown-out Reset is immediately activated. When V
(V
expired.
The BOD circuit will only detect a drop in V
ger than t
Figure 18. Brown-out Reset During Operation
BOT+
BOT+
= V
in
BOD
BOT
Figure
CC
+ V
given in
INTERNAL
TIME-OUT
HYST
18), the delay counter starts the MCU after the time-out period t
RESET
RESET
V
CC
/2 and V
Table 15 on page
Table 15 on page
BOT-
CC
TOUT
decreases to a value below the trigger level (V
= V
has expired.
BOT
V
BOT-
38.
- V
RST
CC
HYST
if the voltage stays below the trigger level for lon-
38) will generate a reset, even if the clock is not
on its positive edge, the delay counter starts the
/2.
CC
V
t
TOUT
BOT+
increases above the trigger level
CC
BOT-
2486Z–AVR–02/11
level during
TOUT
in
Figure
has