Note that I believe that 0x30000000 is the base address of the TSE MAC register space, 0x30100000 is the base address of the SGDMA control, and that 0x30300000 is the base address of the SGDMA descriptor as shown below: (gdb) p tse_ptr->currdescriptor_ptr $33 = (alt_sgdma_descriptor *) 0x30300040 (gdb) step Breakpoint 8, tse_mac_aRxRead (mi=0x4008f7e0, rxDesc=0x30300040) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/drivers/src/altera_avalon_tse.c:140 Now, just before pinging the board: (gdb) x/100 0x30000000 0x30000000: 0x00000a00 0x00000000 0x0400020b 0xffed0700 0x30000010: 0x0000ffff 0x000005ee 0x00000000 0x000007f0 0x30000020: 0x00000000 0x000007f0 0x00000000 0x00000008 0x30000030: 0x00000008 0x00000008 0x00000003 0x00000000 0x30000040: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000050: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000060: 0xffed0700 0x0000ffff 0x00000000 0x00000009 0x30000070: 0x00000000 0x00000000 0x00000000 0x000002e5 0x30000080: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000090: 0x00000000 0x00000009 0x00000000 0x00000000 0x300000a0: 0x00000000 0x00000000 0x00000000 0x00000000 0x300000b0: 0x00000387 0x00000009 0x00000000 0x00000000 0x300000c0: 0x00000000 0x00000009 0x00000000 0x00000000 0x300000d0: 0x00000000 0x00000000 0x00000000 0x00000000 0x300000e0: 0x00000000 0x00000000 0x00040000 0x02000000 0x300000f0: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000100: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000110: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000120: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000130: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000140: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000150: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000160: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000170: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000180: 0x00000000 0x00000000 0x00000000 0x00000000 just after pinging the board: (gdb) x/100 0x30000000 0x30000000: 0x00000a00 0x00000000 0x0400020b 0xffed0700 0x30000010: 0x0000ffff 0x000005ee 0x00000000 0x000007f0 0x30000020: 0x00000000 0x000007f0 0x00000000 0x00000008 0x30000030: 0x00000008 0x00000008 0x00000003 0x00000000 0x30000040: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000050: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000060: 0xffed0700 0x0000ffff 0x00000000 0x0000000d 0x30000070: 0x00000000 0x00000000 0x00000000 0x00000435 0x30000080: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000090: 0x00000004 0x00000009 0x00000000 0x00000000 0x300000a0: 0x00000000 0x00000000 0x00000000 0x00000000 0x300000b0: 0x0000051f 0x0000000d 0x00000000 0x00000000 0x300000c0: 0x00000000 0x0000000d 0x00000000 0x00000000 0x300000d0: 0x00000000 0x00000000 0x00000000 0x00000000 0x300000e0: 0x00000000 0x00000000 0x00040000 0x02000000 0x300000f0: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000100: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000110: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000120: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000130: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000140: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000150: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000160: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000170: 0x00000000 0x00000000 0x00000000 0x00000000 0x30000180: 0x00000000 0x00000000 0x00000000 0x00000000 (gdb) x/60 0x30300000 0x30300000: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300010: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300020: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300030: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300040: 0x00000000 0x00000000 0x40093814 0x00000000 0x30300050: 0x30300060 0x00000000 0x00000000 0x00800069 0x30300060: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300070: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300080: 0x00000000 0x00000000 0x00000000 0x00000000 0x30300090: 0x00000000 0x00000000 0x00000000 0x00000000 0x303000a0: 0x00000000 0x00000000 0x00000000 0x00000000 0x303000b0: 0x00000000 0x00000000 0x00000000 0x00000000 0x303000c0: 0x00000000 0x00000000 0x00000000 0x00000000 0x303000d0: 0x00000000 0x00000000 0x00000000 0x00000000 0x303000e0: 0x00000000 0x00000000 0x00000000 0x00000000 (gdb) x/60 0x30100000 0x30100000: 0x0000000e 0x00000000 0x00000000 0x00000000 0x30100010: 0x00000068 0x00000000 0x00000000 0x00000000 0x30100020: 0x30300040 0x00000000 0x00000000 0x00000000 0x30100030: 0x00000000 0x00000000 0x00000000 0x00000000 0x30100040: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x30100050: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x30100060: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x30100070: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x30100080: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x30100090: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x301000a0: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x301000b0: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x301000c0: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x301000d0: 0xffffffff 0xffffffff 0xffffffff 0xffffffff 0x301000e0: 0xffffffff 0xffffffff 0xffffffff 0xffffffff (gdb) x/60 0x40093814 0x40093814: 0x33330000 0xfb000000 0x18fc5000 0xdd86300d 0x40093824: 0x00000060 0xff113100 0x000080fe 0x00000000 0x40093834: 0xfffc5002 0x300d18fe 0x000002ff 0x00000000 0x40093844: 0x00000000 0xfb000000 0xe914e914 0x9b153100 0x40093854: 0x00000000 0x00000100 0x00000000 0x31333103 0x40093864: 0x30013001 0x07303102 0x612d6e69 0x04726464 0x40093874: 0x61707261 0x000c0000 0x00000001 0x00000000 0x40093884: 0x00000000 0x00000000 0x00000000 0x00000000 0x40093894: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938a4: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938b4: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938c4: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938d4: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938e4: 0x00000000 0x00000000 0x00000000 0x00000000 0x400938f4: 0x00000000 0x00000000 0x00000000 0x00000000 (gdb) where #0 alt_avalon_sgdma_do_async_transfer (dev=0x40009364, desc=0x30300040) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/drivers/src/altera_avalon_sgdma.c:149 #1 0x00435bc4 in tse_mac_aRxRead (mi=0x4008f7e0, rxDesc=0x30300040) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/drivers/src/altera_avalon_tse.c:163 #2 0x0041b2d8 in tse_sgdma_read_init (tse_ptr=0x4008f7dc) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/drivers/src/iniche/ins_tse_mac.c:749 #3 0x0041ad70 in tse_mac_init (iface=0) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/drivers/src/iniche/ins_tse_mac.c:500 #4 0x0041ba4c in Netinit () at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/iniche/src/ip/ipnet.c:148 #5 0x0041c850 in ip_startup () at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/iniche/src/ip/ipstart.c:137 #6 0x0043ad30 in netmain_init () at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/iniche/src/allports/allports.c:372 #7 0x0041f3e0 in tk_netmain (parm=0x0) at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/iniche/src/misclib/netmain.c:298 #8 0x00435580 in OSStartTsk () at c:/altera/10.0/nios2eds/examples/verilog/niosII_cycloneIII_3c120/triple_speed_ethernet_design/software/niosII_simple_socket_server_hack2_0_bsp/HAL/src\os_cpu_a.S:268