System verilog 大型SystemVerilog约束的示例

你能举一个大而复杂的SystemVerilog约束的例子吗？越大越好，最好是现实的。也许一些地址计算也依赖于一些其他变量

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我正在评估将我们的IP转换为使用SystemVerilog约束，我的管理层希望了解创建/理解SystemVerilog约束有多容易/难。

这里有一个示例，可能不太大也不复杂，但它应该让您了解如何使用约束。在这里，您将看到使用了以下概念：

随机数和随机数-循环和非循环随机变量

两种类型的分布式约束

使用蕴涵运算符在约束内使用if条件。。。根据另一个变量计算的地址

约束顺序求解器

约束构造函数中随机变量的默认范围

在约束中使用枚举类型

希望这有助于。。。并注意在线评论：

class RandomConstraints;
    enum IpVersionType {IPV4=2, IPV6, IPVx}

    //Randomly iterate over values without repetition
    randc bit [7:0] cyclicCounter;
    //Regular random variables
    rand bit [15:0] destAddress;
    rand bit [15:0] sourceAddress;
    rand bit [15:0] numberOfPackets;
    rand bit [15:0] packetLength;
    rand bit [7:0]  var1;
    rand bit [7:0]  var2;
    IpVersionType ipVersion;

    //Non-random variables that can be used to control constraints
    bit [15:0] minNumberOfPackets, maxNumberOfPackets;
    bit [15:0] minPacketLength, maxPacketLength;
    integer IPV4Weight, IPV6Weight;

    constraint cPacketLength {
        packetLength in { minPacketLength : maxPacketLength }
    }
    constraint cChannelNumber {
        channelNumber in {0:1}
    }
    constraint cIPVersionType {
        ipVersion dist { IPV4 := IPV4Weight, IPV6 := IPV6Weight, IPVX := (100 - IPV4Weight - IPV6Weight) }
    }
    //Probability of var1 being 1,2,3,4,5 in the ratio 1,2,4,4,4
    constraint cDist1 {
        var1 dist { 1 := 1, 2 := 2, [3:4] := 4 }
    }
    //Probability of var2 being 1,2,3,4,5 is in the ratio 1,2,4/3,4/3,4/3 
    constraint cDist2 {
        var2 dist { 1 := 1, 2 := 2, [3:5] :/ 4 }
    }       
    //Implication constraint - if(channelNum == i) then { ... }
    constraint cImplication {
        (channelNumber == 0) => {
            destAddress in {0:200};
            sourceAddress in {201:400};
        }
        (channelNumber == 1) => {
            destAddress in {201:400};
            sourceAddress in {0:200};
        }
    }
    //Controlling order of constraints solved using a constraint solver
    constraint order_solver {
        solver channelNumber before destAddress;
        solver channelNumber before sourceAddress;
    }

    function new();
        //Setting default min/max packets and min/max packet length
        minNumberOfPackets = 100;
        maxNumberOfPackets = 1000;
        minPacketLength = 128;
        maxPacketLength = 256;
        IPV4Weight = 50;
        IPV6Weight = 30;
    endfunction
endclass

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由于我无法对上一篇文章发表评论，并且我建议的编辑被拒绝，我只能添加看起来像新答案但不是的内容。唉

下面是Subbdue的示例，该示例经过编辑以修复以下语法错误：

SV

typedef枚举{…}与OpenVera相反的语法<代码>枚举{…}语法

使用

结束枚举声明

声明变量

channelNumber

将

ipVersion

声明为

rand

SV

在{[：]}

语法中，与{min:max}语法中的OpenVera

相反

用

结束
约束中的表达式
s

SV

->

语法与OpenVera

=>

语法相反

修复打字错误

solver

->

solve

修复键入

IPVx

->

IPVx

固定示例：

class RandomConstraints;
    typedef enum {IPV4=2, IPV6, IPVX} IpVersionType;

    //Randomly iterate over values without repetition
    randc bit [7:0] cyclicCounter;
    //Regular random variables
    rand bit [15:0] destAddress;
    rand bit [15:0] sourceAddress;
    rand bit [15:0] numberOfPackets;
    rand bit [15:0] packetLength;
    rand bit [3:0] channelNumber;
    rand bit [7:0]  var1;
    rand bit [7:0]  var2;
    rand IpVersionType ipVersion;

    //Non-random variables that can be used to control constraints
    bit [15:0] minNumberOfPackets, maxNumberOfPackets;
    bit [15:0] minPacketLength, maxPacketLength;
    integer IPV4Weight, IPV6Weight;

    constraint cPacketLength {
        packetLength inside { [ minPacketLength : maxPacketLength ] };
    }
    constraint cChannelNumber {
        channelNumber inside {[0:1]};
    }
    // Assuming total weight adds up to 100
    constraint cIPVersionType {
        ipVersion dist { IPV4 := IPV4Weight, IPV6 := IPV6Weight,
          IPVX := (100 - IPV4Weight - IPV6Weight) };
    }
    //Probability of var1 being 1,2,3,4,5 in the ratio 1,2,4,4,4
    constraint cDist1 {
        var1 dist { 1 := 1, 2 := 2, [3:4] := 4 };
    }
    //Probability of var2 being 1,2,3,4,5 is in the ratio 1,2,4/3,4/3,4/3
    constraint cDist2 {
        var2 dist { 1 := 1, 2 := 2, [3:5] :/ 4 };
    }
    //Implication constraint - if(channelNum == i) then { ... }
    constraint cImplication {
        (channelNumber == 0) -> {
            destAddress inside {[0:200]};
            sourceAddress inside {[201:400]};
        }
        (channelNumber == 1) -> {
            destAddress inside {[201:400]};
            sourceAddress inside {[0:200]};
        }
    }
    //Controlling order of constraints solved using a constraint solver
    constraint order_solver {
        solve channelNumber before destAddress;
        solve channelNumber before sourceAddress;
    }

    function new();
        //Setting default min/max packets and min/max packet length
        minNumberOfPackets = 100;
        maxNumberOfPackets = 1000;
        minPacketLength = 128;
        maxPacketLength = 256;
        IPV4Weight = 50;
        IPV6Weight = 30;
    endfunction
endclass

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干得好看起来，我需要2千分才能有资格审查建议的编辑（即使是在我自己的帖子上：）。。既然你煞费苦心地写了一篇新文章，我就不写了。