[avr-gcc-list] Using external RAM

[Shubham Jain]

Hello,

Where is the size of the external ram specified using avr-gcc? How do I
use pointers to external memory?

Thanking you,
Shubham Jain

Hello,

In order to have pointers to XMEM, please go through some embedded 'C' books. The heap size mentioned by you will be used to allocate memory if you make a call to that function. Please read the GCC LIB manual for more details. Please do not send only personal mails. It is better to include the gcc list as you will receive more responses to your queries.

 

Nayani

Shubham Jain <address@hidden> wrote:

Hello,
Thanks for the reply.

Where is the size of the xram specified?

Secondly, how do I use pointers to xmem? Is the detail available anywhere?

Thanking you,
Shubham Jain
>
>
> Shubham Jain wrote:
>
>>You are saying that under programme control I can enable and/or disable
>>external RAM. Does this mean more than setting SRE in MCUCR.
>
>>Secondly, I have not declared the available RAM from 2000H to 3fffH. That
>>is the declaration of dynamic memory heap as I understood from the
>>avr-libc user manual.
>
>
> External RAM can be turned on/off by setting and clearing the SRE bit in
> MCUCR register.
> Depending on the HW design, sometimes the port pins are used as IO pins
> and sometimes as address data bus. In such ! casses the SRE bit is
> dynamically controlled through programme.
>
>>From your linker script I see you setting the xram address. Whatever be
>> your programming language (assembly/c) if you have pointers to xmem,
>> these settings do not really matter as you can access extmem by using the
>> pointer(s). This is really low level of programming.
>
> Nayani
>
>
>
>
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