AT90USB646 datasheet(78/456 Pages) ATMEL

78 / 456 page

7593L–AVR–09/12

AT90USB64/128

11.3.1

MCUCR – MCU Control Register

• Bit 4 – PUD: Pull-up Disable

When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn and

PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01). See “Con-

figuring the pin” on page 72 for more details about this feature.

11.3.2

Alternate functions of Port A

The Port A has an alternate function as the address low byte and data lines for the External

Memory Interface.

Table 11-4 and Table 11-5 on page 79 relates the alternate functions of Port A to the overriding

signals shown in Figure 11-5 on page 76.

Bit

JTD

–

–PUD

–

IVSEL

IVCE

MCUCR

Read/write

R/W

Initial value

Table 11-3.

Port A pins alternate functions.

Port pin

Alternate function

PA7

AD7 (External memory interface address and data bit 7)

PA6

AD6 (External memory interface address and data bit 6)

PA5

AD5 (External memory interface address and data bit 5)

PA4

AD4 (External memory interface address and data bit 4)

PA3

AD3 (External memory interface address and data bit 3)

PA2

AD2 (External memory interface address and data bit 2)

PA1

AD1 (External memory interface address and data bit 1)

PA0

AD0 (External memory interface address and data bit 0)

Table 11-4.

Overriding signals for alternate functions in PA7..PA4.

Signal

name

PA7/AD7

PA6/AD6

PA5/AD5

PA4/AD4

PUOE

SRE

PUOV

~(WR | ADA (1)) •

PORTA7 • PUD

~(WR | ADA) •

PORTA6 • PUD

~(WR | ADA) •

PORTA5 • PUD

~(WR | ADA) •

PORTA4 • PUD

DDOE

SRE

DDOV

WR | ADA

PVOE

SRE

PVOV

A7 • ADA | D7

OUTPUT • WR

A6 • ADA | D6

OUTPUT • WR

A5 • ADA | D5

OUTPUT • WR

A4 • ADA | D4

OUTPUT • WR

DIEOE

DIEOV

D7 INPUTD6 INPUTD5 INPUTD4 INPUT

AIO

–

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