icebling_snippet2.v

icebling_snippet2.v

// handle state machine
case (curr_state)

    sSTART:
        begin 
            // start new frame
            curr_state <= sNEW_FRAME;
        end

    sNEW_FRAME:
        begin 
            // start new frame
            if (!cnewframe)
                begin
                    // copy grid
                    grid_cpy <= grid;

                    // reset current position
                    i <= 0;

                    // change state to compute sum
                    curr_state <= sCOMPUTE_8NN;
                end
        end

    sUPDATE:
        begin 

            // increment position 
            i <= i + 1;

            // set grid value based on sum
            if (grid[i])
                begin 
                    if (sum < 2 || sum > 3)
                        begin 
                            grid[i] <= 0;
                        end
                end 
            else if (sum == 3) 
                begin 
                    grid[i] <= 1;   
                end
            
            // done with frame?
            if (i == 63)
                begin 
                    // go to new frame
                    curr_state <= sNEW_FRAME;
                end
            else 
                begin 
                    // reset sum
                    sum <= 0;
                    // change state to compute
                    curr_state <= sCOMPUTE_8NN;
                end
        end

    sCOMPUTE_8NN:
        begin 
            // automatic toroidal boundary conditions because of 
            // index overflow
            sum <=  grid_cpy[i-N-1] + grid_cpy[i-N] + 
                    grid_cpy[i-N+1] + 
                    grid_cpy[i-1] + grid_cpy[i+1] + 
                    grid_cpy[i+N-1] + grid_cpy[i+N] + 
                    grid_cpy[i+N+1];

            // change state to update
            curr_state <= sUPDATE;
        end

    default:
        curr_state <= sSTART;

endcase