at43usb355 ATMEL Corporation, at43usb355 Datasheet - Page 67

• Manufacturer Part Number: at43usb355
• Description: At43usb355 Full-speed Usb Microcontroller With Embedded Hub, Adc And Pwm
• Manufacturer: ATMEL Corporation

PortA as General
Digital I/O
2603G–USB–04/06
Port A Data Register – PORTA
Port A Data Direction Register – DDRA
Port A Input Pins Address – PINA
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 Port A Data Latch is read, and
when reading PINA, the logical values present on the pins are read.
All 8 pins in Port A have equal functionality 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 config-
ured as an input pin. If PORTAn is set (one) when the pin is 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) or the pin has to configured as an output pin. The Port A pins are tri-stated
when a reset condition becomes active, even if the clock is not active.
Table 24. DDAn Effects on Port A Pins
Note:
Initial Value
Read/Write
Initial Value
Read/Write
Initial Value
Read/Write
$1B ($3B)
$1A ($3A)
$19 ($39)
Bit
Bit
Bit
DDAn
0
0
1
1
n: 7,6...0, pin number.
PORTA7
PINA7
DDA7
R/W
R/W
N/A
R
7
0
7
0
7
PORTAn
PORTA6
0
1
0
1
PINA6
DDA6
R/W
R/W
N/A
6
0
R
6
0
6
PORTA5
PINA5
DDA5
R/W
R/W
N/A
5
0
5
0
5
R
Output
Output
Input
Input
I/O
PORTA4
PINA4
DDA4
R/W
R/W
N/A
R
4
0
4
0
4
Comment
Tri-state (Hi-Z)
PAn will source current if ext. pulled low.
Push-Pull Zero Output
Push-Pull One Output
PORTA3
PINA3
DDA3
R/W
R/W
N/A
3
0
R
3
0
3
PORTA2
PINA2
DDA2
R/W
R/W
N/A
R
2
0
2
0
2
AT43USB355
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
DDRA
PINA
PORTA
67