AT91 datasheet(20/153 Pages) ATMEL

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AT91X40 Series

1354D–ATARM–08/02

External Bus Interface Pin Description

The following table shows how certain EBI signals are multiplexed:

Name

Description

Type

A0 - A23

Address bus (output)

Output

D0 - D15

Data bus (input/output)

I/O

NCS0 - NCS3

Active low chip selects (output)

Output

CS4 - CS7

Active high chip selects (output)

Output

NRD

Read enable (output)

Output

NWR0 - NWR1

Lower and upper write enable (output)

Output

NOE

Output enable (output)

Output

NWE

Write enable (output)

Output

NUB, NLB

Upper and lower byte select (output)

Output

NWAIT

Wait request (input)

Input

Table 4. EBI Signals

Multiplexed Signals

Functions

A23 - A20

CS4 - CS7

Allows from 4 to 8 chip select lines to be used

NLB

8- or 16-bit data bus

NRD

NOE

Byte write or byte select access

NWR0

NWE

Byte write or byte select access

NWR1

NUB

Byte write or byte select access

AT91 Datasheet(PDF) 20 Page - ATMEL Corporation

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