SystemVerilog -- 2.5 Data Types ~ SystemVerilog Packed Arrays

SystemVerilog Packed Arrays

SystemVerilog 中有两种类型的数组- packed array 和 unpacked array。

packed array用于引用在变量名称之前声明的维度。

bit [3:0] data;        // Packed array or vector
logic     queue [9:0]; // unpacked array

packed array保证表示为一组连续的位。它们只能用于单位数据类型（如、和其他递归packed array）组成。bit logic

Single Dimensional Packed Arrays

一维压缩数组也成为向量。

module tb;
  bit [7:0]  m_data;    // A vector or 1D packed array
  initial begin
    // 1. Assign a value to the vector
    m_data = 8'hA2;
    // 2. Iterate through each bit of the vector and print value
    for (int i = 0; i < $size(m_data), i++) begin
      $display ("m_data[%0d] = %b", i, m_data[i]);
    end
  end
endmodule

Muultidimensional Packed Arrays

多维打包数组仍然是一组连续的位，但也被分割成更小的组。

Example #1

下面显示的代码声明一个占用32位或4个字节的2D打包数组，并循环访问段并打印其值。

module tb;
  bit [3:0][7:0]    m_data;    // A MDA, 4 bytes

  initial begin
    // 1. Assign a value to the MDA
    m_data = 32'hface_cafe;
    $display ("m_data = 0x%0h", m_data);
    // 2. Iterate through each segment of the MDA and print value
    for (int i = 0; i < $size(m_data); i++) begin
      $display("m_data[%0d] = %b (0x%0h)", i, m_data[i], m_data[i]);
    end
  end
endmodule

模拟日志

ncsim> run
m_data = 0xfacecafe
m_data[0] = 11111110 (0xfe)
m_data[1] = 11001010 (0xca)
m_data[2] = 11001110 (0xce)
m_data[3] = 11111010 (0xfa)
ncsim: *W,RNQUIE: Simulation is complete.

Example #2

现在让我们看一个3D packed array

module tb;
  bit [2:0][3:0][7:0]   m_data;  // An MDA, 12 bytes
  
  initial begin
    // 1. Assign a value to the MDA
    m_data[0] = 32'hface_cafe;
    m_data[1] = 32'h1234_5678;
    m_data[2] = 32'hc0de_fade;
    // m_data gets a packed value
    $display ("m_data = 0x%0h", m_data);

    // 2. Iterate through each segment of the MDA and print value
    foreach (m_data[i]) begin
      $display ("m_data[%0d] = 0x%0h", i, m_data[i]);
      foreach (m_data[i][j]) begin
        $display ("m_data[%0d][%0d] = 0x%0h", i, j, m_data[i][j]);
      end
    end
  end
endmodule

模拟日志

ncsim> run
m_data = 0xc0defade12345678facecafe
m_data[2]    = 0xc0defade
m_data[2][3] = 0xc0
m_data[2][2] = 0xc0
m_data[2][1] = 0xc0
m_data[2][0] = 0xc0
m_data[1] = 0x12345678
m_data[1][3] = 0x12
m_data[1][2] = 0x34
m_data[1][1] = 0x56
m_data[1][0] = 0x78
m_data[1] = 0x12345678
m_data[0][3] = 0xfa
m_data[0][2] = 0xce
m_data[0][1] = 0xca
m_data[0][0] = 0xfe
ncsim: *W,RNQUIE: Simulation is complete.