大型SystemVerilog约束的示例

Question

你能给出一个大而复杂的SystemVerilog约束的例子吗？越大越好,最好是现实的.也许某些地址计算也取决于其他一些变量.

我正在评估切换我们的IP以使用SystemVerilog约束,我的管理层希望看到创建/理解SystemVerilog约束是多么容易/多难.

Answer 1

由于我无法评论上一篇文章,我的建议编辑被拒绝,我只能添加看起来像新答案但不是.叹!

以下是编辑Subbdue的示例以修复以下语法错误:

1. SV typedef enum {...} <name>;语法而不是OpenVera enum <name> {...};语法
2. 结束枚举声明 ;
3. 声明变量 channelNumber
4. 声明ipVersion为rand
5. SV <var> inside { [<min>:<max>] }语法而不是OpenVera <var> in { min:max }语法
6. constraints中的结束表达式;
7. SV ->语法而不是OpenVera =>语法
8. 修正拼写错误solver- >solve
9. 修正拼写错误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