atmega323l ATMEL Corporation, atmega323l Datasheet - Page 139

• Manufacturer Part Number: atmega323l
• Description: Atmega323 8-bit Avr Microcontroller With 32k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Port B
The Port B Data Register –
PORTB
The Port B Data Direction
Register – DDRB
The Port B Input Pins Address
– PINB
1457G–AVR–09/03
Port B is an 8-bit bi-directional I/O port with optional internal pull-ups.
Three I/O Memory address locations are allocated for Port B, one each for the Data
Register – PORTB, $18($38), Data Direction Register – DDRB, $17($37) and the Port B
Input Pins – PINB, $16($36). The Port B Input Pins address is read only, while the Data
Register and the Data Direction Register are read/write.
All port pins have individually selectable pull-up resistors. The Port B output buffers can
sink 20 mA and thus drive LED displays directly. When pins PB0 to PB7 are used as
inputs and are externally pulled low, they will source current if the internal pull-up resis-
tors are activated.
The Port B pins with alternate functions are shown in Table 49.:
Table 49. Port B Pins Alternate Functions
When the pins are used for the alternate function, the DDRB and PORTB Registers
have to be set according to the alternate function description.
Bit
$18 ($38)
Read/Write
Initial Value
Bit
$17 ($37)
Read/Write
Initial Value
Bit
$16 ($36)
Read/Write
Initial Value
Port Pin
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
PORTB7
PINB7
DDB7
R/W
R/W
N/A
R
7
0
7
0
7
Alternate Functions
T0 (Timer/Counter 0 External Counter Input)
XCK (USART External Clock Input/Output)
T1 (Timer/Counter 1 External Counter Input)
AIN0 (Analog Comparator Positive Input)
INT2 (External Interrupt 2 Input)
AIN1 (Analog Comparator Negative Input)
OC0 (Timer/Counter0 Output Compare Match Output)
SS (SPI Slave Select Input)
MOSI (SPI Bus Master Output/Slave Input)
MISO (SPI Bus Master Input/Slave Output)
SCK (SPI Bus Serial Clock)
PORTB6
PINB6
DDB6
R/W
R/W
N/A
R
6
0
6
0
6
PORTB5
PINB5
DDB5
R/W
R/W
N/A
R
5
0
5
0
5
PORTB4
PINB4
DDB4
R/W
R/W
N/A
R
4
0
4
0
4
PORTB3
PINB3
DDB3
R/W
R/W
N/A
3
0
3
0
3
R
PORTB2
PINB2
DDB2
R/W
R/W
N/A
2
0
2
0
2
R
ATmega323(L)
PORTB1
PINB1
DDB1
R/W
R/W
N/A
R
1
0
1
0
1
PORTB0
PINB0
DDB0
R/W
R/W
N/A
R
0
0
0
0
0
PORTB
DDRB
PINB
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