ATmega8535 Atmel Corporation, ATmega8535 Datasheet - Page 52

• Manufacturer Part Number: ATmega8535
• Manufacturer: Atmel Corporation

Specifications of ATmega8535

• Flash (kbytes): 8 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 3
• 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): 0.5
• 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: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Ports as General Digital
I/O
Configuring the Pin
52
ATmega8535(L)
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 23 shows a
functional description of one I/O-port pin, here generically called Pxn.
Figure 23. General Digital I/O
Note:
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
“Register Description for I/O-Ports” on page 66, the DDxn bits are accessed at the
DDRx I/O address, the 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 config-
ured as an input pin.
If PORTxn is written a 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 a logic one when the pin is configured as an output pin, the port pin
is driven high (one). If PORTxn is written a logic zero when the pin is configured as an
output pin, the port pin is driven low (zero).
When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn,
PORTxn} = 0b11), an intermediate state with either pull-up enabled ({DDxn, PORTxn} =
Pxn
1. WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clk
SLEEP, and PUD are common to all ports.
PUD:
SLEEP:
clk
I/O
:
PULLUP DISABLE
SLEEP CONTROL
I/O CLOCK
(1)
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
RESET
RESET
PORTxn
Q
Q
Q
Q
DDxn
CLR
CLR
D
D
2502K–AVR–10/06
PUD
WDx
RDx
WPx
RPx
clk
RRx
I/O
I/O
,