AT90USB646 datasheet(37/459 Pages) ATMEL

부품명	AT90USB646

상세설명	8-bit Microcontroller with 64/128K Bytes of ISP Flash and USB Controller

PDF	459 Pages

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제조업체	ATMEL [ATMEL Corporation]

홈페이지	http://www.atmel.com

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37 / 459 page

7593H–AVR–11/08

ATmega32U6/AT90USB64/128

Figure 5-10. Address Map with 32 KB External Memory

5.5.9

Using all 64KB Locations of External Memory

Since the External Memory is mapped after the Internal Memory as shown in Figure 5-4, only

56KB of External Memory is available by default (address space 0x0000 to 0x20FF is reserved

for internal memory). However, it is possible to take advantage of the entire External Memory by

masking the higher address bits to zero. This can be done by using the XMMn bits and control

by software the most significant bits of the address. By setting Port C to output 0x00, and releas-

ing the most significant bits for normal Port Pin operation, the Memory Interface will address

0x0000 - 0x2FFF. See the following code examples.

Care must be exercised using this option as most of the memory is masked away.

x0000

x20FF

xFFFF

x2100

x7FFF

x8000

x0000

x7FFF

emory Configuration A

nternal Memory

nused)

AVR M

emory Map

xternal 32K S RAM

xternal

emory

XMem start + 0x8000

ISRAM end + 0x8000

XMem start

ISRAM end

AT90USB646 데이터시트(PDF) 37 Page - ATMEL Corporation