at90ls4433 ATMEL Corporation, at90ls4433 Datasheet - Page 72

• Manufacturer Part Number: at90ls4433
• Description: At90s4433 8-bit Avr Microcontroller With 4k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

I/O Ports
Port B
Port B Data Register – PORTB
Port B Data Direction Register
– DDRB
Port B Input Pins Address –
PINB
72
AT90S/LS4433
All AVR ports have true Read-Modify-Write functionality when used as general digital
I/O ports. This means that the direction of one port pin can be changed without uninten-
tionally changing the direction of any other pin with the SBI and CBI instructions. The
same applies for changing drive value (if configured as output) or enabling/disabling of
pull-up resistors (if configured as input).
Port B is a 6-bit bi-directional I/O port.
Three I/O memory address locations are allocated for the 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 23.
Table 23. Port B Pin 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
R
R
R
0
7
–
0
7
–
0
7
–
Alternate Functions
ICP (Timer/Counter1 Input Capture Pin)
OC1 (Timer/Counter1 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)
R
R
R
0
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
R
3
0
3
0
3
PORTB2
PINB2
DDB2
R/W
R/W
N/A
R
2
0
2
0
2
PORTB1
PINB1
DDB1
R/W
R/W
N/A
R
1
0
1
0
1
PORTB0
PINB0
DDB0
R/W
R/W
N/A
1042H–AVR–04/03
0
0
0
0
0
R
PORTB
DDRB
PINB