at90ls8535-8mi ATMEL Corporation, at90ls8535-8mi Datasheet - Page 76

• Manufacturer Part Number: at90ls8535-8mi
• Description: 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

I/O Ports
Port A
Port A Data Register – PORTA
Port A Data Direction Register
– DDRA
Port A Input Pins Address –
PINA
76
AT90S/LS8535
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 unintention-
ally 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.
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; this address enables access to
the physical value on each Port A pin. When reading PORTA, the Port A Data Latch is
read and when reading PINA, the logical values present on the pins are read.
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
R
6
0
6
0
6
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 power-down 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
R
2
0
2
0
2
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
1041H–11/01
PORTA
DDRA
PINA