topic Re: Need to declare variables in external SDRAM as well in the internal RAM. in LPC Microcontrollers

Need to declare variables in external SDRAM as well in the internal RAM.

billbrown — Sun, 25 Dec 2016 03:11:53 GMT

I am using an LPC2468 processor with external SDRAM starting at address 0xa000000 in addition to the the processors built in RAM. I am using Kiel uVision. I need to define variables in both address spaces.

Do I need to define each variable using the __attribute__ modifier? If so, how?

Is there a way to say, from here until I say otherwise use this memory space or the other ? Or does each variable need its own qualifier?

I have played with the scatter allocation file but looking at the map file variables are still allocated in unexpected places/

Thanks

Re: Need to declare variables in external SDRAM as well in the internal RAM.

CarlosCasillas — Wed, 04 Jan 2017 19:41:40 GMT

Hi Bill,

You could take a look at the following links, which seems to be related to what are you trying:

https://www.lpcware.com/content/forum/allocating-dynamic-memory-external-sdram

https://www.lpcware.com/content/forum/could-i-use-extern-sdram-ram

https://community.nxp.com/thread/429937

Hope this will be useful for you.
Best regards!
/Carlos
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Re: Need to declare variables in external SDRAM as well in the internal RAM.

converse — Thu, 05 Jan 2017 12:40:23 GMT

Kiel docs how to do this

ARM: LOCATING VARIABLES AT ABSOLUTE MEMORY ADDRESSES