HDLBits-Rule110

Rule 110 is a one-dimensional cellular automaton with interesting properties (such as being Turing-complete).

There is a one-dimensional array of cells (on or off). At each time step, the state of each cell changes. In Rule 110, the next state of each cell depends only on itself and its two neighbours, according to the following table:

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

(The name "Rule 110" comes from reading the "next state" column: 01101110 is decimal 110.)

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 Declaration

module top_module(
    input clk,
    input load,
    input [511:0] data,
    output [511:0] q
); 

本题主要是根据真值表写出逻辑表达式，观察 next state 0比较少，因此写出0的表达式，最后取反即可 。

注意化简表达式。

module top_module(
    input clk,
    input load,
    input [511:0] data,
    output [511:0] q
); 
    always @(posedge clk) begin
        if(load)begin 
            q <= data;
        end
        else begin 
            q <= ~(({1'b0,q[511:1]} & {q[511:0]} & {q[510:0],1'b0}) 
                   |(~q[511:0] & ~{q[510:0],1'b0}));
        end
    end
endmodule