AT91 datasheet(25/153 Pages) ATMEL

25 / 153 page

AT91X40 Series

1354D–ATARM–08/02

Byte Select Access is used to connect 16-bit devices in a memory page.

•

The signal A0/NLB is used as NLB and enables the lower byte for both read and

write operations.

•

The signal NWR1/NUB is used as NUB and enables the upper byte for both read

and write operations.

•

The signal NWR0/NWE is used as NWE and enables writing for byte or half word.

•

The signal NRD/NOE is used as NOE and enables reading for byte or half word.

Figure 12 shows how to connect a 16-bit device with byte and half-word access (e.g. 16-

bit SRAM) on NCS2.

Figure 12. Connection for a 16-bit Data Bus with Byte and Half-word Access

Figure 13 shows how to connect a 16-bit device without byte access (e.g. Flash) on

NCS2.

Figure 13. Connection for a 16-bit Data Bus without Byte Write Capability.

EBI

D0 - D7

D8 - D15

A1 - A19

NLB

NWE

NOE

NCS2

D0 - D7

D8 - D15

A0 - A18

Low Byte Enable

Write Enable

Output Enable

Memory Enable

NUB

High Byte Enable

EBI

D0 - D7

D8 - D15

A1 - A19

NLB

NWE

NOE

NCS2

D0 - D7

D8 - D15

A0 - A18

Write Enable

Output Enable

Memory Enable

NUB

AT91 Datasheet(PDF) 25 Page - ATMEL Corporation

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