对SPI进行参数化结构设计

前言

为了避免每次SPI驱动重写，直接参数化，尽量一劳永逸。

SPI master有啥用呢，你发现各种外围芯片的配置一般都是通过SPI配置的，只不过有3线和四线。

SPI slave有啥用呢，当外部主机（cpu）要读取FPGA内部寄存器值，那就很有用了，fpga寄存器就相当于RAM，cpu通过SPI寻址读写数据。

代码仅供参考，勿做商业用途。

SPI salve

SPI salve支持功能：（1）支持三线SPI或者四线SPI。通过define切换。

（2）支持指令长度、帧长自定义。

（3）工作时钟可自定义，大于SPI clk的2倍。

用户只需修改：（1）几线SPI。（2）单帧长度。（3）指令长度。（4）寄存器开辟。

注意：指令最高bit表示读写，低写高读，其余bit表示地址。指令接着为数据端，两者位宽之和即为SPI单帧长。

//`define SPI_LINE  //是否是三线SPI
`define SPI_FRAME_WIDTH  //SPI一帧长度为16
`define SPI_INS_WIDTH     //SPI指令长
`timescale 1ns/1ps
////
module spi_slave
(
    input     i_clk               , //work clk
    input     i_rst_n             ,  
 
    input     i_spi_clk           , //SPI clk
    input     i_spi_cs            , //SPI cs
 
    `ifdef SPI_LINE                 //条件编译
    inout     io_spi_sdio
    `else
    input     i_spi_mosi          , //SPI mosi
    output    o_spi_miso            //SPI miso
    `endif
);
//位宽计算函数
function integer clogb2 (input integer depth);
begin
    for (clogb2=; depth>; clogb2=clogb2+)
        depth = depth >>;
end
endfunction
reg r_cs = 'b1; //打一拍
always @(posedge i_clk)
begin
    r_cs <= i_spi_cs;
end
reg [:] r_spi_clk_edge = 'b00; //SPI clk边沿检测
always @(posedge i_clk)
begin
    r_spi_clk_edge <= {r_spi_clk_edge[],i_spi_clk};
end //always
reg [clogb2(`SPI_FRAME_WIDTH-)-:] r_spi_cnt = 'd0;
always @(posedge i_clk)
begin
    if (r_cs) //cs为高则归零
        r_spi_cnt <= 'd0;
    else if (r_spi_clk_edge == 'b10) //下降沿才计数
        r_spi_cnt <= r_spi_cnt + 'd1;
end
////指令锁存
reg [`SPI_INS_WIDTH-:] r_ins = 'd0;
always @(posedge i_clk)
begin
    if ((~r_cs) && (r_spi_clk_edge == 'b01)) //上升沿锁存数据
    begin
        if ((r_spi_cnt >= ) && (r_spi_cnt <= `SPI_INS_WIDTH-))
        `ifdef SPI_LINE                 //条件编译
            r_ins <= {r_ins[`SPI_INS_WIDTH-:],io_spi_sdio};
        `else
            r_ins <= {r_ins[`SPI_INS_WIDTH-:],i_spi_mosi};
        `endif
    end
end
////数值写入
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_data_rx = 'd0;
always @(posedge i_clk)
begin
    if ((~r_cs) && (r_spi_clk_edge == 'b01)) //上升沿锁存数据
    begin
        if (r_spi_cnt >= `SPI_INS_WIDTH)
        `ifdef SPI_LINE
            r_data_rx <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:],io_spi_sdio};
        `else
            r_data_rx <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:],i_spi_mosi};
        `endif
    end
end
////用户寄存器定义
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_reg0 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_reg1 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_reg2 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_reg3 = 'd0;
////
always @(posedge i_clk,negedge i_rst_n)
begin
    if (~i_rst_n)
    begin
        r_reg0 <= 'd0;
        r_reg1 <= 'd0;
        r_reg2 <= 'd0;
        r_reg3 <= 'd0;
 
    end
    else if ((~r_ins[`SPI_INS_WIDTH-]) && (r_spi_cnt == (`SPI_FRAME_WIDTH-)) && (~r_cs) && (r_spi_clk_edge == 'b01))
    begin
    `ifdef SPI_LINE
        case (r_ins[`SPI_INS_WIDTH-:])
            'd0:begin r_reg0 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
            'd1:begin r_reg1 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
            'd2:begin r_reg2 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
            'd3:begin r_reg3 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
 
        endcase
    `else
        case (r_ins[`SPI_INS_WIDTH-:])
            'd0:begin r_reg0 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
            'd1:begin r_reg1 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
            'd2:begin r_reg2 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
            'd3:begin r_reg3 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
 
        endcase
    `endif
    end
 
end
////寄存器值读出
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:] r_data_tx = 'd0;
always @(posedge i_clk)
begin
    if (r_ins[`SPI_INS_WIDTH-] && (~r_cs) && (r_spi_clk_edge == 'b10))
    begin
        if (r_spi_cnt == (`SPI_INS_WIDTH-))
        begin
            case (r_ins[`SPI_INS_WIDTH-:])
                'd0:begin r_data_tx <= r_reg0; end
                'd1:begin r_data_tx <= r_reg1; end
                'd2:begin r_data_tx <= r_reg2; end
                'd3:begin r_data_tx <= r_reg3; end 
 
            endcase
        end
        else
            r_data_tx <= {r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-:],'b0};
    end
end
 
////读取输出
`ifdef SPI_LINE
assign io_spi_sdio = (r_ins[`SPI_INS_WIDTH-]) ? (((r_spi_cnt>=`SPI_INS_WIDTH) && (r_spi_cnt<`SPI_FRAME_WIDTH)) ? r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-] : 'bz) : 1'bz;
`else
assign o_spi_miso = ((r_spi_cnt>=`SPI_INS_WIDTH) && (r_spi_cnt<`SPI_FRAME_WIDTH)) ? r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-] : 'b0;
`endif
 
endmodule // end the spi_slave model

SPI master

spi master内部仅仅封装SPI驱动，写入值读出控制由上层控制，这部分逻辑很simple，不赘述。用户只需给入SPI帧及控制使能即可。

用户只需修改parameter参数：（1）单帧长。（2）指令长。（3）数据长。（4）工作时钟。（5）SPI clk。

实现不使用状态机，采用线性序列计数法。

//`define SPI_LINE  //是否是三线SPI
`timescale 1ns/1ps
module spi_master
#(parameter p_spi_frame_width = , //SPI单帧长度
  parameter p_spi_ins_width =    , //指令长度
  parameter p_spi_data_width =     //读出数据长度
 )
(
    input                                i_clk             , //系统时钟
    input                                i_rst_n           ,
    input                                i_flag            , //检测到flag的上升沿则启动一次传输,一个时钟周期即可
 
    input     [p_spi_frame_width-:]    i_spi_data        ,
    output                               o_spi_cs          ,
    output                               o_spi_clk         ,
 
    `ifdef SPI_LINE                 //条件编译
    inout                                io_spi_sdio       ,
    `else
    input                                i_spi_miso        , //SPI miso
    output                               o_spi_mosi        , //SPI mosi
    `endif 
 
    output                               o_transfer_done   , //单次传输完成
    output    [p_spi_data_width-:]     o_spi_data          //读取数据
);
parameter p_clk_fre = ; //XXM时钟频率
parameter p_spi_clk_fre = 0.5*; //SPI 时钟速率,表示1M
parameter p_clk_div = p_clk_fre * /p_spi_clk_fre/-;
parameter p_spi_cnt_max = p_spi_frame_width*-;
parameter p_spi_ins_max = p_spi_ins_width*-;
//位宽计算函数
function integer clogb2 (input integer depth);
begin
    for (clogb2=; depth>; clogb2=clogb2+)
        depth = depth >>;
end
endfunction
//把最大值赋值给线型，直接用p_clk_div仿真有问题，但实际上板是可以的
wire [clogb2(p_clk_div)-:] w_clk_div;
assign w_clk_div = p_clk_div;
////时钟分频
reg [clogb2(p_clk_div)-:] r_cnt_div = 'd0;
always @(posedge i_clk)
begin
    if (r_cnt_div == w_clk_div)
        r_cnt_div <= 'd0;
    else
        r_cnt_div <= r_cnt_div + 'd1;
end //always
wire w_clk_en; //分频时钟使能
assign w_clk_en = (r_cnt_div == w_clk_div) ? 'b1 : 1'b0;
reg [:] r_flag_edge = 'b00;
reg [clogb2(p_spi_cnt_max)-:] r_spi_cnt = 'd0;
always @(posedge i_clk) //flag边沿检测
begin
    r_flag_edge <= {r_flag_edge[],i_flag};
end
//flag信号展宽到低速时钟域
reg r_flag_enlarge = 'b0;
always @(posedge i_clk)
begin
    if (r_flag_edge == 'b01) //上升沿拉高
        r_flag_enlarge <= 'b1;
    else if (r_spi_cnt == p_spi_ins_max) //足够长的高电平才拉低
        r_flag_enlarge <= 'b0;
end
reg [:] r_flag_enlarge_edge = 'b00;
always @(posedge i_clk)
begin
    if (w_clk_en)
        r_flag_enlarge_edge <= {r_flag_enlarge_edge[],r_flag_enlarge};
end
reg r_cs = 'b1;
always @(posedge i_clk)
begin
    if (w_clk_en)
    begin
        if (r_flag_enlarge_edge == 'b01) //检测到需要进行SPI操作
            r_cs <= 'b0;
        else if (r_spi_cnt == p_spi_cnt_max) //计数到最大值表示一次SPI完成
            r_cs <= 'b1;
    end
end
always @(posedge i_clk)
begin
    if (w_clk_en)
    begin
        if(~r_cs) //在操作区间计数
            r_spi_cnt <= r_spi_cnt + 'd1;
        else
            r_spi_cnt <= 'd0;
    end
end
////数据传输段
reg [p_spi_frame_width-:] r_data = 'd0;
always @(posedge i_clk)
begin
    if (w_clk_en)
    begin
        if (r_flag_enlarge_edge == 'b01) //上升沿刷入
            r_data <= i_spi_data;
        else if (r_spi_cnt[] == 'b1) //数据移动
            r_data <= {r_data[p_spi_frame_width-:],'b1};
    end
end
////数据读取段
reg [p_spi_data_width-:] r_data_read = 'd0;
always @(posedge i_clk)
begin
    if (w_clk_en)
    begin
        if (i_spi_data[p_spi_frame_width-] && (r_spi_cnt > p_spi_ins_max) && (r_spi_cnt[] == 'b0)) //是读
        `ifdef SPI_LINE
            r_data_read <= {r_data_read[p_spi_data_width-:],io_spi_sdio};
        `else
            r_data_read <= {r_data_read[p_spi_data_width-:],i_spi_miso};
        `endif
    end
end
////SPI输出段
assign o_spi_cs = r_cs;
assign o_spi_clk = r_cs ? 'b0 : r_spi_cnt[0];
////SPI SDIO的输入输出切换
`ifdef SPI_LINE
assign io_spi_sdio = (i_spi_data[p_spi_frame_width-]) ? (((r_spi_cnt >= 'd0) && (r_spi_cnt <= p_spi_ins_max)) ? r_data[p_spi_frame_width-1] : 1'bz ) : r_data[p_spi_frame_width-];
`else
assign o_spi_mosi = r_data[p_spi_frame_width-];
`endif
assign o_transfer_done = ((~r_cs) && (r_spi_cnt == p_spi_cnt_max)) ? 'b1:1'b0;
assign o_spi_data = r_data_read;
 
endmodule // end the spi_master model

仿真如下所示：写入四个寄存器值，再读出。

仿真代码如下：

`define TRANSFER_NUMBER  //操作数为4
`define DATA 'ha5
//`define SPI_LINE
timeunit 1ns;
timeprecision 1ps;
module top;
parameter p_sim_end_time = ; //ns
logic l_clk = 'b0;
always #2.5 l_clk = ~l_clk;
////复位
logic l_rst_n  = 'b0;
initial begin
    # l_rst_n = 'b1;
end
 
wire io_sdio;
wire o_spi_cs;
wire o_spi_clk;
wire o_transfer_done;
wire [:] o_spi_data;
////多个数据操作模式
reg r_flag = 'b0;
reg [:] r_first_cnt = 'b00;
always @(posedge l_clk,negedge l_rst_n)
begin
    if (~l_rst_n)
        r_first_cnt <= 'b00;
    else if (r_first_cnt == 'd3)
        r_first_cnt <= r_first_cnt;
    else
        r_first_cnt <= r_first_cnt + 'd1;
end
reg [:] r_transfer_done_edge = 'b00;
always @(posedge l_clk)
begin
    r_transfer_done_edge <= {r_transfer_done_edge[],o_transfer_done};
end
reg [:] r_transfer_cnt = 'd0;
always @(posedge l_clk)
begin
    if ((r_first_cnt == 'd2) && (r_transfer_cnt < `TRANSFER_NUMBER))
        r_flag <= 'b1;
    else if ((r_transfer_done_edge == 'b10) && (r_transfer_cnt < `TRANSFER_NUMBER-1))
        r_flag <= 'b1;
    else
        r_flag <= 'b0;
end
always @(posedge l_clk)
begin
    if (r_transfer_done_edge == 'b10)
        r_transfer_cnt <= r_transfer_cnt + 'd1;
end
reg [:] r_in_data  = 'd0;
always @(*)
begin
    if (~l_rst_n) //仿真不执行此段仿真会有问题
        r_in_data  = 'h0000;
    else
    begin
    case(r_transfer_cnt)
        'd0:begin  r_in_data  = {8'h00,'h43}; end
        'd1:begin  r_in_data  = 16'h0132; end
        'd2:begin  r_in_data  = 16'h0245; end
        'd3:begin  r_in_data  = 16'h0367; end
        'd4:begin  r_in_data  = 16'h8000; end
        'd5:begin  r_in_data  = 16'h8100; end
        'd6:begin  r_in_data  = 16'h8200; end
        'd7:begin  r_in_data  = 16'h8300; end 
 
        default:begin  r_in_data  = 'h0000; end
    endcase
    end
end
 
wire w_spi_miso;
wire w_spi_mosi;
 
spi_master inst_spi_master (
    .i_clk             (l_clk),
    .i_rst_n           (),
    .i_flag            (r_flag),
    .i_spi_data        (r_in_data),
    .o_spi_cs          (o_spi_cs),
    .o_spi_clk         (o_spi_clk),
    `ifdef SPI_LINE
    .io_spi_sdio       (io_sdio),
    `else
    .i_spi_miso        (w_spi_miso),
    .o_spi_mosi        (w_spi_mosi),
    `endif
    .o_transfer_done   (o_transfer_done),
    .o_spi_data        (o_spi_data)
 
);
 
spi_slave  inst_spi_slave (
    .i_clk                            (l_clk),
    .i_rst_n                          (l_rst_n),
 
    .i_spi_clk                        (o_spi_clk),
    .i_spi_cs                         (o_spi_cs),
    `ifdef SPI_LINE
    .io_spi_sdio                      (io_sdio)
    `else
    .i_spi_mosi                      (w_spi_mosi),
    .o_spi_miso                      (w_spi_miso)
    `endif
 
);
 
initial begin
    #p_sim_end_time $stop;
end
 
endmodule

三线SPI：

四线SPI：

可以看到读写是一致的，验证通过。

以上。