[HDLBits] Rule90

Rule 90 is a one-dimensional cellular automaton with interesting properties.

The rules are simple. There is a one-dimensional array of cells (on or off). At each time step, the next state of each cell is the XOR of the cell's two current neighbours. A more verbose way of expressing this rule is the following table, where a cell's next state is a function of itself and its two neighbours:

Left	Center	Right	Center's next state
1	1	1	0
1	1	0	1
1	0	1	0
1	0	0	1
0	1	1	1
0	1	0	0
0	0	1	1
0	0	0	0

(The name "Rule 90" comes from reading the "next state" column: 01011010 is decimal 90.)

In this circuit, create a 512-cell system (q[511:0]), and advance by one time step each clock cycle. The load input indicates the state of the system should be loaded with data[511:0]. Assume the boundaries (q[-1] and q[512]) are both zero (off).

module top_module(
    input clk,
    input load,
    input [511:0] data,
    output [511:0] q ); 
    always@(posedge clk) begin
        if(load)
            q<=data;
        else
            q<={1'b0,q[511:1]}^{q[510:0],1'b0};
        //verilog最好的地方就是支持整个数组批量运算
    end
endmodule

verilog真舒服