ahb总线时序verilog实现

下面是一个简单的AHB总线时序Verilog实现的示例：

module ahb_bus(
  input HCLK, // 高速时钟信号
  input HRESETn, // 异步低电平复位信号
  input HSEL, // 总线选择信号
  input [31:0] HADDR, // 总线地址信号
  input HTRANS, // 总线传输类型信号
  input [2:0] HSIZE, // 总线传输大小信号
  input [1:0] HBURST, // 总线突发类型信号
  input [2:0] HPROT, // 总线保护类型信号
  input [3:0] HMASTLOCK, // 总线主控锁定类型信号
  input [31:0] HWDATA, // 总线写数据信号
  input [31:0] HRESP, // 总线响应信号
  output [31:0] HRDATA // 总线读数据信号
);

  // 定义状态机
  localparam IDLE = 2'b00;
  localparam ADDR_PHASE = 2'b01;
  localparam TRANS_PHASE = 2'b10;
  
  reg [1:0] state = IDLE;
  reg [31:0] address;
  reg [31:0] write_data;
  reg [31:0] read_data;
  reg [2:0] size;
  reg [1:0] burst;
  
  // 定义计数器
  reg [2:0] count;
  
  always @(posedge HCLK or negedge HRESETn) begin
    if (!HRESETn) begin
      state <= IDLE;
      count <= 0;
      address <= 0;
      write_data <= 0;
      read_data <= 0;
      size <= 0;
      burst <= 0;
    end else begin
      case (state)
        IDLE: begin
          if (HSEL) begin
            state <= ADDR_PHASE;
            address <= HADDR;
            size <= HSIZE;
            burst <= HBURST;
            case (HTRANS)
              2'b00: count <= 0; // IDLE
              2'b01: count <= 0; // BUSY
              2'b10: count <= size; // NONSEQ
              2'b11: count <= size; // SEQ
            endcase
          end
        end
        ADDR_PHASE: begin
          if (count == 0) begin
            state <= TRANS_PHASE;
            case (HTRANS)
              2'b00: begin // IDLE
                read_data <= 0;
                write_data <= 0;
              end
              2'b01: begin // BUSY
                read_data <= 0;
                write_data <= HWDATA;
              end
              2'b10, 2'b11: begin // NONSEQ, SEQ
                if (burst == 2'b01 || burst == 2'b10) begin // INCR, WRAP4
                  read_data <= 0;
                  write_data <= HWDATA;
                end else begin // FIXED, WRAP8
                  read_data <= 0;
                  write_data <= HWDATA;
                  address <= address + 4;
                  count <= count - 1;
                end
              end
            endcase
          end else begin
            if (burst == 2'b11 && (address & 3) != 0) begin // SEQ, unaligned
              state <= IDLE;
            end else begin
              address <= address + 4;
              count <= count - 1;
            end
          end
        end
        TRANS_PHASE: begin
          if (HRESP[1] == 1) begin // ERROR
            state <= IDLE;
          end else begin
            if (count == 0) begin
              state <= IDLE;
              case (HTRANS)
                2'b00: begin // IDLE
                  read_data <= 0;
                  write_data <= 0;
                end
                2'b01: begin // BUSY
                  read_data <= 0;
                  write_data <= 0;
                end
                2'b10, 2'b11: begin // NONSEQ, SEQ
                  if (burst == 2'b00) begin // FIXED
                    read_data <= HRESP[0] ? HRDATA : 0;
                  end else if (burst == 2'b01) begin // INCR
                    read_data <= HRESP[0] ? HRDATA : 0;
                    address <= address + 4;
                  end else if (burst == 2'b10) begin // WRAP4
                    read_data <= HRESP[0] ? HRDATA : 0;
                    address <= (address[31:2] << 2) | 2'b00;
                  end else if (burst == 2'b11) begin // WRAP8
                    read_data <= HRESP[0] ? HRDATA : 0;
                    address <= (address[31:2] << 2) | 2'b00;
                  end
                end
              endcase
            end else begin
              if (burst == 2'b01 || burst == 2'b10) begin // INCR, WRAP4
                read_data <= HRESP[0] ? HRDATA : 0;
                address <= address + 4;
              end else begin // FIXED, WRAP8
                read_data <= HRESP[0] ? HRDATA : 0;
                address <= address + 4;
                count <= count - 1;
              end
            end
          end
        end
      endcase
    end
  end
  
  assign HRDATA = read_data;
  
endmodule

这个代码模块实现了一个简单的AHB总线时序，它可以连接到其他模块，如存储器或外设。在时钟上升沿时，它根据总线信号的状态更新状态机，并根据总线传输类型和突发类型更新计数器和地址。它还可以读取和写入数据，并在读取操作完成时返回读取的数据。