ATmega162 datasheet(26/324 Pages) ATMEL

26 / 324 page

2513K–AVR–07/09

ATmega162/V

External Memory

Interface

With all the features 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)

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 on page 2, Table 29

on page 70, Table 35 on page 75, and Table 41 on page 81). The memory configuration is

shown in Figure 11.

Figure 11. External Memory with Sector Select

Note:

1. Address depends on the ATmega161 compatibility Fuse. See “SRAM Data Memory” on page

18 and Figure 9 on page 19 for details.

Using the External

Memory Interface

The interface consists of:

•

AD7:0: Multiplexed low-order address bus and data bus

•

A15:8: High-order address bus (configurable number of bits)

•

ALE: Address latch enable

•RD: Read strobe.

•WR: Write strobe.

0x0000

0x04FF/0x045F

(1)

External Memory

(0-64K x 8)

0xFFFF

Internal Memory

SRL[2..0]

SRW11

SRW10

SRW01

SRW00

Lower Sector

Upper Sector

0x0500/0x0460

(1)

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