Rainbow-electronics ATmega161L Manual de usuario descargar pdf (Pagina 100)

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ATmega161(L)

1228C–AVR–08/02

Port D Port D is an 8-bit bi-directional I/O port with internal pull-up resistors.

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

– 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 Reg-

ister and the Data Direction Register are read/write.

The Port D output buffers can sink 20 mA. As inputs, Port D pins that are externally

pulled low will source current if the pull-up resistors are activated.

Some Port D pins have alternate functions as shown in Table 33.

When the PD5 pin is used for the alternate function (OC1A), the DDRD and PORTD

Registers have to be set according to the alternate function description.

Port D Data Register – PORTD

Port D Data Direction Register

– DDRD

Port D Input Pins Address –

PIND

The Port D Input Pins address (PIND) is not a register; this address enables access to

the physical value on each Port D pin. When reading PORTD, the Port D Data Latch is

read and when reading PIND, the logical values present on the pins are read.

Port D as General Digital I/O PDn, general I/O pin: The DDDn bit in the DDRD Register selects the direction of this

pin. If DDDn is set (one), PDn is configured as an output pin. If DDDn is cleared (zero),

PDn is configured as an input pin. If PORTDn is set (one) when configured as an input

pin, the MOS pull-up resistor is activated. To switch the pull-up resistor off, the PORTDn

Table 33. Port D Pin Alternate Functions

Port Pin Alternate Function

PD0 RXD0 (UART0 Input Line)

PD1 TXD0 (UART0 Output Line)

PD2 INT0 (External Interrupt0 Input)

PD3 INT1 (External Interrupt1 Input)

PD3 TOSC1 (RTC Oscillator Timer/Counter2)

PD5

TOSC2 (RTC Oscillator Timer/Counter2)/OC1A (Timer/Counter1 Output

CompareA Match Output)

PD6 WR

(Write Strobe to External Memory)

PD7 RD

(Read Strobe to External Memory)

Bit 76543210

$12 ($32)

PORTD7 PORTD6 PORTD5 PORTD4 PORTD3 PORTD2 PORTD1 PORTD0 PORTD

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$11 ($31) DDD7 DDD6 DDD5 DDD4 DDD3 DDD2 DDD1 DDD0 DDRD

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$10 ($30) PIND7 PIND6 PIND5 PIND4 PIND3 PIND2 PIND1 PIND0 PIND

Read/Write R R R R R R R R

Initial Value N/A N/A N/A N/A N/A N/A N/A N/A

1 2 ... 95 96 97 98 99 100 101 102 103 104 105 ... 158 159

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