Nios II software

Read the part about conduits in the Avalon documentation. You can map a conduit in memory and write and read from it on the Nios side. On the other side, you will have to interpret the signals -- this is very clearly specified in the Avalon documentation. You can start with this module definition...

module conduit    (// Slave interface
                   input csi_clock_clk,
                   input csi_clock_reset_n,
                 
                   input     avs_s1_address,
                   input          avs_s1_read,
                   input          avs_s1_write,
                   input    avs_s1_writedata,
                   output   avs_s1_readdata,
                   output         avs_s1_waitrequest,
                 
                   // Conduit
                   output         coe_user_clk,
                   output         coe_user_reset_n,
                   output    coe_user_address,
                   output         coe_user_read,
                   output         coe_user_write,
                   output   coe_user_writedata,
                   input    coe_user_readdata,
                   input          coe_user_waitrequest);

Please note that the csi, avs, and coe prefixes are needed there so that SOPC can easily interpret what your signals mean. You will need this snippet after you try to create a custom component in SOPC...