Modular sgdma messes with ueser logic writing/reading of SDRAM

Dear all,

I have a Qsys system with PCie, user logic, DDR2 SDRAM. I use user logic to continuously write/read a DDR2 SDRAM. It seems working properly. I use windriver to write/read from DDR2 SDRAM, it seems working properly too.

Now I want to add sgdma to do fast communication between PC and DDR2 SDRAM. After I add sgdma, and connect its to DDR2 SDRAM, the continuously writing/reading seems stop even I don't issue a DMA command yet.

Why the modular sgdma stops/interferes my reading/writing to DDR2 SDRAM using user logic? anyone can give me some advices?

Thank you very much!