axi slave如何处理outstanding

Axi Slave 处理 outstanding 的方式是通过使用 AXI 协议中的 WREADY 信号来通知 Master，表示 Slave 已经准备好接收下一个数据传输。如果 Slave 没有准备好接收下一个数据传输，它可以将 WREADY 信号保持低电平，这将导致 Master 在 AXI 协议中等待，直到 Slave 准备好接收下一个数据传输。

相关问题

verilog AXI slave with outstanding

An AXI slave with outstanding transactions can be implemented in Verilog by using a state machine to manage the response to incoming transactions. The state machine can keep track of the number of outstanding transactions and respond accordingly. Here is an example implementation:

module axi_slave_outstanding(
  input          aclk,
  input          aresetn,
  input          awvalid,
  input  [31:0]  awaddr,
  input  [2:0]   awprot,
  input          awcache,
  input          awburst,
  input  [3:0]   awlen,
  input          arvalid,
  input  [31:0]  araddr,
  input  [2:0]   arprot,
  input          arcache,
  input          arburst,
  input  [3:0]   arlen,
  input          wvalid,
  input  [31:0]  wdata,
  input  [3:0]   wstrb,
  input          wlast,
  output         bvalid,
  output         rvalid,
  output  [1:0]  rresp,
  output  [31:0] rdata,
  output         rlast
);

  reg [1:0] state;
  reg [31:0] mem[0:1023];
  reg [3:0] arcount;
  reg [3:0] awcount;
  
  // Reset state machine and counters on reset
  always @(posedge aclk) begin
    if (!aresetn) begin
      state <= 2'b00;
      arcount <= 4'b0000;
      awcount <= 4'b0000;
    end
  end
  
  // State machine
  always @(posedge aclk) begin
    case (state)
      // Idle state
      2'b00: begin
        if (awvalid) begin
          state <= 2'b01;
          awcount <= awlen;
        end else if (arvalid) begin
          state <= 2'b10;
          arcount <= arlen;
        end
      end
      // Write data state
      2'b01: begin
        if (wvalid) begin
          mem[awaddr] <= wdata;
          awaddr <= awaddr + 1;
          awcount <= awcount - 1;
          if (wlast) begin
            bvalid <= 1'b1;
            state <= 2'b00;
          end
        end
      end
      // Read data state
      2'b10: begin
        if (rcount == 4'b0000) begin
          rvalid <= 1'b1;
          rdata <= mem[araddr];
        end
        araddr <= araddr + 1;
        arcount <= arcount - 1;
        if (arcount == 4'b0000) begin
          rlast <= 1'b1;
          rvalid <= 1'b0;
          state <= 2'b00;
        end
      end
      // Error state
      default: begin
        state <= 2'b00;
      end
    endcase
  end
endmodule

In this implementation, the state machine has three states: idle, write data, and read data. When an AXI write transaction is received, the state machine transitions to the write data state and writes the incoming data to memory. It also keeps track of the number of outstanding write transactions using the `awcount` counter. When an AXI read transaction is received, the state machine transitions to the read data state and reads the requested data from memory. It also keeps track of the number of outstanding read transactions using the `arcount` counter.

The `bvalid`, `rvalid`, `rdata`, and `rlast` outputs are used to signal the completion of the AXI transactions to the master. The `bvalid` output is set to 1 when a write response is ready, and the `rvalid` output is set to 1 when a read response is ready. The `rdata` output contains the read data, and the `rlast` output signals the end of a read transaction.

This implementation assumes a single master and a single slave, and does not support burst transactions or interleaved transactions. It also does not support any AXI extensions beyond the basic read and write transactions.

用sv语言写一个带有outstanding能力大小为10的axi slave class，且能够储存数据

以下是一个简单的例子，展示了如何在SystemVerilog中定义一个带有outstanding能力大小为10的AXI从设备类，并且可以存储数据。

class axi_slave;
  // 定义AXI接口信号
  logic [31:0] araddr, awaddr, rdata, wdata;
  logic [2:0] arprot, awprot;
  logic [1:0] arsize, awsize;
  logic [3:0] arburst, awburst;
  logic arvalid, arready, rvalid, rready;
  logic awvalid, awready, wvalid, wready, bvalid, bready;
  logic [1:0] bresp, rresp;
  // 定义存储数据的寄存器
  logic [31:0] data_reg [0:9];

  // AXI接口方法
  function void read_input();
    // 读取输入端口
  endfunction

  function void write_output();
    // 写入输出端口
  endfunction

  // 初始化方法
  function new();
    // 初始化存储数据的寄存器
    for (int i = 0; i < 10; i++) begin
      data_reg[i] = 0;
    end
  endfunction

  // AXI接口协议方法
  task ar_protocol();
    // 处理读请求
  endtask

  task aw_protocol();
    // 处理写请求
  endtask

  task r_protocol();
    // 发送读响应
  endtask

  task b_protocol();
    // 发送写响应
  endtask
endclass

该类定义了AXI接口的信号和存储数据的寄存器，还定义了一些方法来处理AXI接口协议和初始化存储数据的寄存器。在实际应用中，还需要根据需要添加其他方法和信号。