Multiple Ethernet application under MicroC/OS-II

You don't need a separate DDR: all dma share the same memory. My system is the same as yours: 2 tse, 4 dma a single dram; the only difference being I'm using sdram controller, not ddr.

I can't tell you what that error is due to. Try check in sopc builder:

- connections between dma and ddr

- interrupts, arbitration,base addresses

- ddr module configuration

Then in Quartus, if you use top level schematic, check if any connection is missing or if a couple of them has been wrongly connected together.

About socket programming.

One ip address for each Ethernet port (you must define the get_ip_addr() function which will be called by interniche upon initialization)

One socket for each tcp/udp connection you need.

The tcp/ip stack will take care to move data to and from the correct physical Ethernet port.