Access DDR2 memory outside of NIOS SOPC system

[Altera_Forum]

Hi all. 

 I have an SOPC system where my NIOS uses an external DDR2 memory as its main memory. The system being designed is that the NIOS will create an overlay buffer for an 800X600 OnScreen Display. This buffer is stored inside the DDR2 of the NIOS.  The question is, how can a module external to the SOPC system read that overlay buffer?  If the OnScreen Display would need to be refreshed at a 30Hz rate, then we'd need to use a very fast datapath through this DDR2.  Any thoughts?  Thank you

[Altera_Forum]

You need a DMA. You can either add a ready made DMA controller core to your SOPC system (such as Altera's SGDMA) or design your own component that uses an Avalon Master Memory Mapped interface to directly read from the RAM.