题解 | #根据状态转移图实现时序电路#

`timescale 1ns/1ns

module seq_circuit(
   input                C   ,
   input                clk ,
   input                rst_n,
 
   output   wire        Y   
);

localparam  s0  =   2'b00       ;
localparam  s1  =   2'b01       ;
localparam  s2  =   2'b10       ;
localparam  s3  =   2'b11       ;

reg     [1:0]       current_state       ;
reg     [1:0]       next_state          ;

always@(posedge clk or negedge rst_n)begin
    if(!rst_n)
        current_state <= s0;
    else 
        current_state <= next_state;
end

always@(*)begin
    case(current_state)
        s0:begin
            if(C == 1)
                next_state = s1;
            else 
                next_state = s0;
        end
        s1:begin
            if(C == 1)
                next_state = s1;
            else 
                next_state = s3;
        end
        s2:begin
            if(C == 1)
                next_state = s2;
            else 
                next_state = s0;
        end
        s3:begin
            if(C == 1)
                next_state = s2;
            else 
                next_state = s3;
        end
        default:next_state <= s0;
    endcase
end

reg     y_temp      ;
always@(*)begin
    // if(!rst_n)
    //     Y <= 1'b0;
    // else begin
        case(current_state)
            s0:begin
                if(C == 1)
                    y_temp <= 1'b0;
                else 
                    y_temp <= 1'b0;
            end
            s1:begin
                if(C == 1)
                    y_temp <= 1'b0;
                else 
                    y_temp <= 1'b0;
            end
            s2:begin
                if(C == 1)
                    y_temp <= 1'b1;
                else 
                    y_temp <= 1'b0;
            end
            s3:begin
                if(C == 1)
                    y_temp <= 1'b1;
                else 
                    y_temp <= 1'b1;
            end
            default:y_temp <= 1'b0;
        endcase
    end
// end
assign Y = y_temp;
endmodule

y应该是随着状态的变化而变化，而不是随着时钟上升沿变化，这样会得出错误的驱动物理意义