atmega163l ATMEL Corporation, atmega163l Datasheet - Page 115

• Manufacturer Part Number: atmega163l
• Description: Atmega163 8-bit Avr Microcontroller With 16k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

I/O Ports
Port A
The Port A Data Register –
PORTA
The Port A Data Direction
Register – DDRA
The Port A Input Pins Address
– PINA
PORT A as General Digital I/O
1142E–AVR–02/03
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 A is an 8-bit bi-directional I/O port with internal pull-ups.
Three I/O memory address locations are allocated for Port A, one each for the Data
Register – PORTA, $1B($3B), Data Direction Register – DDRA, $1A($3A) and the Port
A Input Pins – PINA, $19($39). The Port A 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 A output buffers
can sink 20 mA and thus drive LED displays directly. When pins PA0 to PA7 are used as
inputs and are externally pulled low, they will source current if the internal pull-up resis-
tors are activated.
Port A has an alternate function as analog inputs for the ADC. If some Port A pins are
configured as outputs, it is essential that these do not switch when a conversion is in
progress. This might corrupt the result of the conversion.
During Power-down mode, the schmitt trigger of the digital input is disconnected. This
allows analog signals that are close to V
causing excessive power consumption.
The Port A Input Pins Address – PINA – is not a register, and this address enables
access to the physical value on each Port A pin. When reading PORTA the PORTA
Data Latch is read, and when reading PINA, the logical values present on the pins are
read.
All 8 bits in PORT A are equal when used as digital I/O pins.
PAn, General I/O pin: The DDAn bit in the DDRA Register selects the direction of this
pin, if DDAn is set (one), PAn is configured as an output pin. If DDAn is cleared (zero),
PAn is configured as an input pin. If PORTAn is set (one) when the pin configured as an
input pin, the MOS pull up resistor is activated. To switch the pull up resistor off, the
PORTAn has to be cleared (zero), the pin has to be configured as an output pin, or the
Bit
$1B ($3B)
Read/Write
Initial Value
Bit
$1A ($3A)
Read/Write
Initial Value
Bit
$19 ($39)
Read/Write
Initial Value
PORTA7
PINA7
DDA7
R/W
R/W
N/A
R
7
0
7
0
7
PORTA6
PINA6
DDA6
R/W
R/W
N/A
6
0
6
0
6
R
PORTA5
PINA5
DDA5
R/W
R/W
N/A
R
5
0
5
0
5
PORTA4
PINA4
DDA4
R/W
R/W
N/A
R
4
0
4
0
4
CC
/2 to be present during powerdown without
PORTA3
PINA3
DDA3
R/W
R/W
N/A
R
3
0
3
0
3
PORTA2
PINA2
DDA2
R/W
R/W
N/A
2
0
2
0
2
R
ATmega163(L)
PORTA1
PINA1
DDA1
R/W
R/W
N/A
R
1
0
1
0
1
PORTA0
PINA0
DDA0
R/W
R/W
N/A
R
0
0
0
0
0
PORTA
DDRA
PINA
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