第三节 FPGA数码管驱动２

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先附上代码：

module Nixie (LEDs ,Nixies,clk,rst);output [7:0] LEDs;output [6:0] Nixies;input  clk,rst;reg [26:0] cnt;reg [6:0] NixieDisplay;reg [7:0] GE;parameter     segment0  = 8'd1,    segment1  = 8'd2,    segment2  = 8'd3,    segment3  = 8'd4,    segment4  = 8'd5,    segment5  = 8'd6,    segment6  = 8'd7,    segment7  = 8'd8,    segment8  = 8'd9,    segment9  = 8'd10,    segment10 = 8'd11,    segment11  = 8'd12,    segment12  = 8'd13,    segment13  = 8'd14,    segment14  = 8'd15,    segment15  = 8'd16;parameter     duan0  = 8'Hc0,    duan1  = 8'HF9,    duan2  = 8'HA4,    duan3  = 8'HB0,    duan4  = 8'H99,    duan5  = 8'H92,    duan6  = 8'H82,    duan7  = 8'HF8,    duan8  = 8'H80,    duan9  = 8'H90,    duan10 = 8'H88,    duan11 = 8'H83,    duan12 = 8'Hc6,    duan13 = 8'Ha1,    duan14 = 8'H86,    duan15 = 8'H8e;always @(posedge clk or negedge rst)    begin         if(!rst)                 begin                    cnt = 0;                    GE  = 0;                end        else             begin                cnt = cnt + 27'b1;                if(cnt >= 27'H2FAF080)                     begin                         cnt = 0;                        GE = GE + 8'b1;                        if(GE == 8'd16) GE = 0;                    end             end     endalways @(posedge clk)    begin        case(GE)            segment0:  NixieDisplay = duan0[6:0];            segment1:  NixieDisplay = duan1[6:0];            segment2:  NixieDisplay = duan2[6:0];            segment3:  NixieDisplay = duan3[6:0];            segment4:  NixieDisplay = duan4[6:0];            segment5:  NixieDisplay = duan5[6:0];            segment6:  NixieDisplay = duan6[6:0];            segment7:  NixieDisplay = duan7[6:0];            segment8:  NixieDisplay = duan8[6:0];            segment9:  NixieDisplay = duan9[6:0];            segment10: NixieDisplay = duan10[6:0];            segment11: NixieDisplay = duan11[6:0];            segment12: NixieDisplay = duan12[6:0];            segment13: NixieDisplay = duan13[6:0];            segment14: NixieDisplay = duan14[6:0];            segment15: NixieDisplay = duan15[6:0];            default:  NixieDisplay = duan0[6:0];        endcase    end    assign Nixies = NixieDisplay;    assign LEDs  = GE;endmodule

先定义数码管的每段的输出：output [6:0] Nixies;再定义时钟和复位按键输入：input  clk,rst;定义计数器CNT的寄存器：   reg [26:0] cnt;（因为使用的是25M的时钟，所以每次时钟反转的时间应该为1/25us，经计算需要 27'H2FAF080次才能到达1s）。因程序用到了case_endcase,所以定义了进入case的条件，类似C里面的数组或者宏定义。

parameter     segment0  = 8'd1,    segment1  = 8'd2,    segment2  = 8'd3,    segment3  = 8'd4,    segment4  = 8'd5,    segment5  = 8'd6,    segment6  = 8'd7,    segment7  = 8'd8,    segment8  = 8'd9,    segment9  = 8'd10,    segment10 = 8'd11,    segment11  = 8'd12,    segment12  = 8'd13,    segment13  = 8'd14,    segment14  = 8'd15,    segment15  = 8'd16;

因数码管显示数字需要按照数码管的格式进行显示，开发板上用到的是共阳极数码管所以直接到查找相关的码表。

parameter     duan0  = 8'Hc0,    duan1  = 8'HF9,    duan2  = 8'HA4,    duan3  = 8'HB0,    duan4  = 8'H99,    duan5  = 8'H92,    duan6  = 8'H82,    duan7  = 8'HF8,    duan8  = 8'H80,    duan9  = 8'H90,    duan10 = 8'H88,    duan11 = 8'H83,    duan12 = 8'Hc6,    duan13 = 8'Ha1,    duan14 = 8'H86,    duan15 = 8'H8e;

复位程序

always @(posedge clk or negedge rst)    begin         if(!rst)                 begin                    cnt = 0;                    GE  = 0;                end        else

假如rst有下降沿进入always并判断此时的rst是否为低电平，假如是的话对计数和码值进行复位。

            begin                cnt = cnt + 27'b1;                if(cnt >= 27'H2FAF080)                     begin                         cnt = 0;                        GE = GE + 8'b1;                        if(GE == 8'd16) GE = 0;                    end             end

计数器不停的计数，到达1S清零并对ＧＥ加一。通过判断GE的值来case 相应的程序。

always @(posedge clk)    begin        case(GE)            segment0:  NixieDisplay = duan0[6:0];            segment1:  NixieDisplay = duan1[6:0];            segment2:  NixieDisplay = duan2[6:0];            segment3:  NixieDisplay = duan3[6:0];            segment4:  NixieDisplay = duan4[6:0];            segment5:  NixieDisplay = duan5[6:0];            segment6:  NixieDisplay = duan6[6:0];            segment7:  NixieDisplay = duan7[6:0];            segment8:  NixieDisplay = duan8[6:0];            segment9:  NixieDisplay = duan9[6:0];            segment10: NixieDisplay = duan10[6:0];            segment11: NixieDisplay = duan11[6:0];            segment12: NixieDisplay = duan12[6:0];            segment13: NixieDisplay = duan13[6:0];            segment14: NixieDisplay = duan14[6:0];            segment15: NixieDisplay = duan15[6:0];            default:  NixieDisplay = duan0[6:0];        endcase    end

判断相应的GE赋值给显示缓存寄存器NixieDisplay。

    assign Nixies = NixieDisplay;    assign LEDs  = GE;

把缓存寄存器的值放到输出ｗｉｒｅ上。

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