AnsweredAssumed Answered

Properly accessing SDRAM

Question asked by Mathieu on Sep 9, 2010
Latest reply on Sep 9, 2010 by reginaldStjohn

Hi all,

I am using an ADSP-21369 DSP with an external SDRAM.

It is stated in the 2136X Processor Hardware Reference Manual that SIMD instructions should not be used to access external SDRAM. I have checked this by toggling the "SIMD disable" check box in the project i use. When checked, accesses are always corrects (Reads and Writes), when unchecked improper writes may occur if a SIMD instruction accesses external SDRAM.

Also, it is stated in the VisualDSP++ 5.0 RTL Manual that the read_extmem and write_extmem specific functions should be use to access external memory in a proper way.

The thing is those functions are not available for 21369 DSP.

Hence my questions :

- Why are both these functions not available for the 21369 ?

- Apart DMA, how can i properly access the external SDRAM knowing that i'd like to keep the SIMD compiler option turned on ?

 

Thanks in advance to those who can help

 

mathieu

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