1. 状态变量设置

localparam IDLE = 6'b00_0001;

localparam GEN_DCLK = 6'b00_0010;

localparam ACK = 6'b00_0100;

这里采用状态独热编码（One-Hot Encoding）

在 FPGA 开发中，独热编码能简化组合逻辑、提升时序性能

2. 两段式状态机，明晰跳转条件

3. 采用end_cnt_clk和end_cnt_num结合的方式方便时序控制，准确进行clk_div的分频

4. 仿真效果展示

仿真上板通过 

 5. 全部代码

module spi_driver1(input                               clk                        ,input                               rst                        ,input                               MISO                       ,output reg                          MOSI                       ,// 1input                               CPOL                       ,input                               CPHA                       ,input              [   7:0]         data_in                    ,output reg         [   7:0]         data_out                   ,//input              [  15:0]         clk_div                    ,output                              nCS                        ,// 1input                               nCTRL                      ,output reg                          DCLK                       ,// 1input                               wr_req                     ,output                              wr_ack                      // 1
);localparam IDLE     = 6'b00_0001;
localparam GEN_DCLK = 6'b00_0010;
localparam ACK      = 6'b00_0100;reg [5:0]cstate;
reg [5:0]nstate;reg [25:0]cnt_clk;
reg [7:0]cnt_num;
reg [7:0]num;wire [15:0]MAX_CNT = clk_div;
wire add_cnt_clk = cstate != IDLE;
wire end_cnt_clk = add_cnt_clk && cnt_clk == MAX_CNT - 1;
wire add_cnt_num = end_cnt_clk;
wire end_cnt_num = add_cnt_num && cnt_num == num - 1;
assign nCS = nCTRL;
assign wr_ack = cstate == ACK && end_cnt_clk;always @(posedge clk or posedge rst) beginif(rst)begincnt_clk <= 26'd0;end else if(add_cnt_clk)beginif(end_cnt_clk)cnt_clk <= 26'd0;else cnt_clk <= cnt_clk + 26'd1;end 
endalways @(posedge clk or posedge rst) beginif(rst)begincnt_num <= 8'd0;end else if(add_cnt_num)beginif(end_cnt_num)cnt_num <= 8'd0;else cnt_num <= cnt_num + 8'd1;end 
endreg [8*20-1:0]state_name;
always @(*) begincase (cstate)IDLE    :begin num = 1;  state_name = "IDLE    "; endGEN_DCLK:begin num = 8;  state_name = "GEN_DCLK"; endACK     :begin num = 1;  state_name = "ACK     "; enddefault :begin num = 1;  state_name = "IDLE    "; endendcase
endwire IDLE_GEN_DCLK  = (cstate == IDLE)      && wr_req           ;
wire GEN_DCLK_ACK   = (cstate == GEN_DCLK)  && end_cnt_num      ; 
wire ACK_IDLE       = (cstate == ACK)       && end_cnt_num      ; always @(posedge clk or posedge rst) beginif(rst)beginDCLK <= (CPOL == 1'b0)?1'b0:1'b1;end else if(cstate == GEN_DCLK && (cnt_clk == MAX_CNT/2 - 1 || cnt_clk == MAX_CNT - 1))beginDCLK <= ~DCLK;end
endreg flag_mosi;
always @(posedge clk or posedge rst) beginif(rst)beginMOSI <= 1'b0;flag_mosi <= 1'b0;end else if(cstate == GEN_DCLK)beginif(CPOL == 1'b0 && cnt_clk == 0)beginMOSI <= data_in[7 - cnt_num];flag_mosi <= 1'b1;end else if(CPOL == 1'b1 && cnt_clk == MAX_CNT/2 - 1)beginMOSI <= data_in[7 - cnt_num];flag_mosi <= 1'b1;end else begin flag_mosi <= 1'b0;endend else if(cstate == ACK)beginMOSI <= 1'b0;flag_mosi <= 1'b0;end 
endreg flag_data_out;
always @(posedge clk or posedge rst) beginif(rst)begindata_out <= 8'd0;flag_data_out <= 1'b0;end else if(cstate == GEN_DCLK)beginif(CPOL == 1'b0 && cnt_clk == MAX_CNT/2 - 1)begindata_out <= {data_out[6:0],MISO};flag_data_out <= 1'b1;end else if(CPOL == 1'b1 && cnt_clk == MAX_CNT - 1)begindata_out <= {data_out[6:0],MISO};flag_data_out <= 1'b1;end else beginflag_data_out <= 1'b0;endend else beginflag_data_out <= 1'b0;end
endalways @(posedge clk or posedge rst) beginif(rst)begincstate <= IDLE;end else begincstate <= nstate;end
endalways @(*) begincase (cstate)IDLE    :if(IDLE_GEN_DCLK)nstate = GEN_DCLK;else nstate = cstate;GEN_DCLK:if(GEN_DCLK_ACK)nstate = ACK;else nstate = cstate;ACK     :if(ACK_IDLE)nstate = IDLE;else nstate = cstate;default :nstate = IDLE;endcase
endendmodule