杂谈：DC对Verilog和SystemVerilog语言的支持

设计语言用哪种？

1. 直接抛出结论：先有电路，后为描述。
2. 设计端而言，没有语言的高低好坏，只有描述的精准与否。本文的实验结果很好的说明了这一点。

Design Compiler对二者的支持

1. 我们在Design Compiler中读入命令有这样的选项，支持包括v和sv在内的三种主流硬件描述语言。
   

简单的fsm电路测试

1. 分别给出一个简单的FSM电路的V代码和SV代码。并基于SAED32nm学习用工艺库来做DCT的实现。
   代码如下

module fsm(
    clk,
    rst_n,
    x,
    y
);
input  clk;
input  rst_n;
input  x;
output y;

parameter A = 3'd0,
          B = 3'd1,
          C = 3'd2,
          D = 3'd3,
          E = 3'd4;

reg [2:0] cur_state,nxt_state;

always @ (posedge clk or negedge rst_n) begin
    if (!rst_n) begin
        cur_state <= A;
    end
    else begin
        cur_state <= nxt_state;
    end
end

always @(*) begin
    if (!rst_n) begin
        nxt_state = A;
    end
    else begin
        case (cur_state) 
        A : if (x) 
                nxt_state = C;
            else 
                nxt_state = B;
        B : if (x) 
                nxt_state = D;
            else 
                nxt_state = B;
        C : if (x) 
                nxt_state = C;
            else 
                nxt_state = E;
        D : if (x) 
                nxt_state = C;
            else 
                nxt_state = E;
        E : if (x) 
                nxt_state = D;
            else 
                nxt_state = B;
        default: nxt_state = A;
    endcase
    end
end

assign y = (cur_state == D) | (cur_state == E);

endmodule

module fsm(
    clk,
    rst_n,
    x,
    y
);
input logic clk;
input logic rst_n;
input logic x;
output logic y;

typedef enum logic [2:0] {A,B,C,D,E} State;

State cur_state,nxt_state;

always_ff @ (posedge clk or negedge rst_n) begin
    if (!rst_n) begin
        cur_state <= A;
    end
    else begin
        cur_state <= nxt_state;
    end
end

always_comb begin
    if (!rst_n) begin
        nxt_state = A;
    end
    else begin
        case (cur_state) 
            A : if (x) 
                    nxt_state = C;
                else 
                    nxt_state = B;
            B : if (x) 
                    nxt_state = D;
                else 
                    nxt_state = B;
            C : if (x) 
                    nxt_state = C;
                else 
                    nxt_state = E;
            D : if (x) 
                    nxt_state = C;
                else 
                    nxt_state = E;
            E : if (x) 
                    nxt_state = D;
                else 
                    nxt_state = B;
            default: nxt_state = A;
        endcase

    end
end

assign y = (cur_state == D) | (cur_state == E);

endmodule

测试结果对比

1. 我们对二者进行相同的综合环境设置并读入设计
   
2. 分析结果如下：
   sv电路图结果如图所示:
   
   v电路图描述结果如下图所示：
   

写在最后

1. 从上一节的结果来看，综合工具DC对两种语言的支持都是比较完美的，因此还是回归那句话，先有电路，后为描述。