AT43USB353M datasheet(55/95 Pages) ATMEL

55 / 95 page

AT43USB353M

3307B–USB–4/04

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.

PortA as General

Digital I/O

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.

Note:

n: 7,6...0, pin number.

Port D

Port D is a 7-bit bi-directional I/O port. Its output buffers can sink or source 2 mA.

Three I/O memory address locations are allocated for the Port D, one each for the Data Regis-

ter - PORTD, $12($32), Data Direction Register (DDRD), $11($31) and the Port D Input Pins

(PIND), $10($30). The Port D 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. When pins PD0 to PD7 are used as

inputs and are externally pulled low, they will source current if the internal pull-up resistors are

activated

Some Port D pins have alternate functions as shown in Table 25.

When the pins are used for the alternate function the DDRD and PORTD register has to be set

according to the alternate function description.

Bit

654

$19 ($39)

PINA7

PINA6

PINA5

PINA4

PINA3

PINA2

PINA1

PINA0

PINA

Read/Write

Initial Value

N/A

Table 24. DDAn Effects on Port A Pins

DDAn

PORTAn

I/O

Comment

Input

Tri-state (Hi-Z)

Input

PAn will source current if ext. pulled low.

Output

Push-Pull Zero Output

Output

Push-Pull One Output

Table 25. Port D Alternate Functions

Port Pin

Alternate Function

PD2

INT0, External Interrupt 0

PD3

INT1, External Interrupt 1

PD4

ICP, Timer/Counter, Input Capture

PD5

OC1A Timer/Counter1 Output Compare A

PD6

OC1B Timer/Counter1 Output Compare B

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