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Registered: ‎12-08-2008

LWIP executing from SRAM

I'm just posting what I learned so that it might benefit the community.  If you want to execute LWIP applications without DDR2 you must be aware of the following:


  • The architecture only offers SDMA connectivity between DDR2 and the TEMAC.  If don't want to have DDR2 memory, then you must use the xps_ll_fifo to allow non-DMA access to the TEMAC.  It is fairly simple to add this fifo to the XPS project.  LWIP software detects the change from SDMA to FIFO automatically.
  • When updating the SDK linker script to assign program sections to SRAM, be aware that SRAM_C_MEM1_BASEADDR is actually a flash device!  (I'm talking about the ML507 board)  You can only assign sections to the SRAM_C_MEM0_BASEADDR which is the 1 Mbyte SRAM.
Here is a somewhat unrelated note regarding running the Raw LWIP demo on a microblaze:   If you get this error message when compiling: 
multiple definition of `_interrupt_handler' 
Disabling relaxation: it will not work with multiple definitions 
Then try removing the xilkernel library from the SDK project build settings.
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