Programming NIOSII interfaced with custom component, using Avalon MM Interface

Hi, the code look like:

always @(posedge csi_clk or posedge rsi_reset_n) begin // To read

if (rsi_reset_n) begin

end else if (avs_s0_read) begin

avs_s0_readdata = START;

end else begin

avs_s0_readdata = 0;

end

end

always @(posedge csi_clk or posedge rsi_reset_n) begin // To write

if (rsi_reset_n) begin

START <= 0;

DATA <= 0;

end else if (avs_s0_write) begin

case (avs_s0_address)

2'b00 : begin//

START <= avs_s0_writedata;

end

2'b01 : begin

DATA <= avs_s0_writedata;

end

default : begin

DATA <= 0;

end

endcase

end

end

In my C ode, i am trying to write START register (as posted previously) and read back START register.

Please suggest. I need to come out of this issue soon