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[avr-gcc-list] Using external RAM

From: Shubham Jain
Subject: [avr-gcc-list] Using external RAM
Date: Tue, 22 Mar 2005 17:22:34 +0530 (IST)
User-agent: SquirrelMail/1.4.3a-1

I came to know from the FAQ that bit SRE (SRAM enable) in the MCUCR
register needs to be set for using external RAM. To do this, I took the
following code from "How to modify MCUCR or WDTCR early?":
;; begin xram.S
#include <avr/io.h>
.section .init1,"ax",@progbits
ldi r16,_BV(SRE) | _BV(SRW)
;; end xram.S

I linked xram.S with other files in my program.

For defining the dynamic memory, I used the following:
avr-gcc ... -Wl,--defsym=__heap_start=0x802000,--defsym=__heap_end=0x803fff

But, I could not understand where is the external RAM specified? Actually,
my requirement is to use external RAM for storing an image which I want to
take as pointer arrays in my program. How should I do this?

Is it necessary to physically connect the external RAM and then do the
testing OR can it be done in software using avr-gcc options?

Yours sincerely,
Shubham Jain

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