ATmega64A datasheet(23/392 Pages) ATMEL

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8160C–AVR–07/09

ATmega64A

7.5

External Memory Interface

With all the features that the External Memory Interface provides, it is well suited to operate as

an interface to memory devices such as external SRAM and Flash, and peripherals such as

LCD-display, A/D, and D/A. The main features are:

• Four different wait-state settings (Including no wait-state).

• Independent wait-state setting for different external memory sectors (configurable sector

size).

• The number of bits dedicated to address high byte is selectable.

• Bus Keepers on data lines to minimize current consumption (optional).

7.5.1

Overview

When the eXternal MEMory (XMEM) is enabled, address space outside the internal SRAM

becomes available using the dedicated external memory pins (see Figure 1-1 on page 2, Table

13-3 on page 75, Table 13-9 on page 79, and Table 13-21 on page 87). The memory configura-

tion is shown in Figure 7-4.

Figure 7-4.

External Memory with Sector Select

(1)

Note:

1. ATmega64A in non ATmega103 compatibility mode: Memory Configuration A is available

(Memory Configuration B N/A).

ATmega64A in mega103 compatibility mode: Memory Configuration B is available (Memory

Configuration A N/A).

Memory Configuration A

0x0000

0x10FF

External Memory

(0-60K x 8)

0xFFFF

Internal Memory

SRL[2..0]

SRW11

SRW10

SRW01

SRW00

Lower Sector

Upper Sector

0x1100

Memory Configuration B

0x0000

External Memory

(0-60K x 8)

0xFFFF

Internal Memory

SRW10

0x0FFF

0x1000

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