ATMEGA640 datasheet(91/449 Pages) ATMEL

91 / 449 page

ATmega640/1280/1281/2560/2561

2549K–AVR–01/07

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 40 and Table 41 relates the alternate functions of Port A to the overriding signals

shown in Figure 36 on page 89.

Note:

1. ADA is short for ADdress Active and represents the time when address is output. See

“External Memory Interface” on page 26 for details.

Table 39. 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 40. 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 INPUT

D6 INPUT

D5 INPUT

D4 INPUT

AIO

–

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