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106

ATmega161(L)

1228C–AVR–08/02

Port E Port E is a 3-bit bi-directional I/O port with internal pull-up resistors.

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

– PORTE, $07($27), Data Direction Register – DDRE, $06($26) and the Port E Input

Pins – PINE, $05($25). The Port E Input Pins address is read-only, while the Data Reg-

ister and the Data Direction Register are read/write.

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

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

Port E pins have alternate functions as shown in Table 35.

Note: 1. When the PE1 pin is used for the alternate function, the DDRE and PORTE Registers

have to be set according to the alternate function description.

Port E Data Register – PORTE

Port E Data Direction Register

– DDRE

Port E Input Pins Address –

PINE

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

the physical value on each Port E pin. When reading PORTE, the Port E Data Latch is

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

Port E as General Digital I/O PEn, general I/O pin: The DDEn bit in the DDRE Register selects the direction of this

pin. If DDEn is set (one), PEn is configured as an output pin. If DDEn is cleared (zero),

PEn is configured as an input pin. If PORTEn is set (one) when configured as an input

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

has to be cleared (zero) or the pin has to be configured as an output pin. The Port E pins

are tri-stated when a reset condition becomes active, even if the clock is not running.

Table 35. Port E Pin Alternate Functions

(1)

Port Pin Alternate Function

PE0 ICP (Input Capture Pin Timer/Counter1)/INT2 (External Interrupt 2 Input)

PE1 OC1B (Timer/Counter1 Output CompareB Match Output)

PE2 ALE (Address Latch Enable, External Memory)

Bit 76543210

$07 ($27)

–––––PORTE2 PORTE1 PORTE0 PORTE

Read/Write RRRRRR/WR/WR/W

InitialValue00000000

Bit 76543210

$06 ($26) –––––DDE2 DDE1 DDE0 DDRE

Read/Write R RRRRR/WR/WR/W

InitialValue00000000

Bit 76543210

$05 ($25) –––––PINE2 PINE1 PINE0 PINE

Read/Write R R R R R R R R

InitialValue00000N/AN/AN/A

1 2 ... 101 102 103 104 105 106 107 108 109 110 111 ... 158 159

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