ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 52

• 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

Ports as General
Digital I/O
Configuring the Pin
52
ATmega8(L)
The ports are bi-directional I/O ports with optional internal pull-ups.
a functional description of one I/O port pin, here generically called Pxn.
Figure 22. General Digital I/O
Note:
Each port pin consists of 3 Register bits: DDxn, PORTxn, and PINxn. As shown in
Description for I/O Ports” on page
PORTxn bits at the PORTx I/O address, and the PINxn bits at the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written logic one,
Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input
pin.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is
activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has to
be configured as an output pin. The port pins are tri-stated when a reset condition becomes
active, even if no clocks are running.
If PORTxn is written logic one when the pin is configured as an output pin, the port pin is driven
high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port
pin is driven low (zero).
Pxn
1. WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clk
and PUD are common to all ports
PUD:
SLEEP:
clk
I/O
:
PULLUP DISABLE
SLEEP CONTROL
I/O CLOCK
(1)
65, the DDxn bits are accessed at the DDRx I/O address, the
SLEEP
SYNCHRONIZER
WDx:
RDx:
WPx:
RRx:
RPx:
D
L
Q
Q
D
PINxn
WRITE DDRx
READ DDRx
WRITE PORTx
READ PORTx REGISTER
READ PORTx PIN
Q
Q
Figure 22 on page 52
RESET
RESET
PORTxn
Q
Q
Q
Q
DDxn
CLR
CLR
D
D
2486Z–AVR–02/11
PUD
WDx
RDx
WPx
RRx
RPx
clk
I/O
I/O
“Register
, SLEEP,
shows