AT43USB325 datasheet(57/109 Pages) ATMEL

57 / 109 page

3355C–USB–4/05

AT43USB325

7.2

Port B

Port B is an 8-bit bi-directional I/O port with open drain outputs and controlled slew rate. It is

designed for use as the column driver in a keyboard controller. The Port B output buffers can

sink or source 4 mA.

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

- PORTB, $18($38), Data Direction Register (DDRB), $17($37) and the Port B Input Pins

(PINB), $16($36). The Port B Input Pins address is read only, while the Data Register and the

Data Direction Register are read/write.

7.2.1

Port B Data Register – PORTB

7.2.2

Port B Data Direction Register – DDRB

7.2.3

Port B Input Pins Address – PINB

The Port B Input Pins address (PINB) is not a register, and this address enables access to the

physical value on each Port B pin. When reading PORTB, the Port B Data Latch is read, and

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

Bit

$18 ($38)

PORTB7

PORTB6

PORTB5

PORTB4

PORTB3

PORTB2

PORTB1

PORTB0

PORTB

Read/Write

R/W

Initial Value

Bit

$17 ($37)

DDB7

DDB6

DDB5

DDB4

DDB3

DDB2

DDB1

DDB0

DDRB

Read/Write

R/W

Initial Value

Bit

$16 ($36)

PINB7

PINB6

PINB5

PINB4

PINB3

PINB2

PINB1

PINB0

PINB

Read/Write

Initial Value

N/A

AT43USB325 Datasheet(PDF) 57 Page - ATMEL Corporation

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