DDPP 课程设计八位 LED 可控移位显示设计与实现本设计基于 Xilinx ISE Design Suite 13.2 软件开发平台和其综合工具进行八位 LED 可控移位显示数字电路的功能设计，在 FPGA BSSYS2 开发板上来完成设计的测试和实现。I、总体 RTL SCHEMATIC端口说明：CLK_IN：50MHZ 时钟输入C：控制左右移，0 为 LED[0]-LED[7]，1 反之。S：选择移动频率，共四档。RST：重置LED：点亮 LED 灯II、源程序module led_shiftingdisplay(LED,CLK_IN,RST,S,C);input CLK_IN,RST,C;input [1:0] S;output [7:0] LED;reg [25:0] cn;reg CLK;reg [7:0] LED;wire CLK_OUT;wire CLK2_OUT;wire CLK3_OUT;wire CLK4_OUT;initial begin cn=0;endalways @(posedge CLK_IN)beginif(cn==49999999)begin cn<=0; endelse cn<=cn+26'd1;endassign CLK_OUT=cn[25];//1HZassign CLK2_OUT=cn[24];//2HZassign CLK3_OUT=cn[21];//16HZassign CLK4_OUT=cn[20];//32HZalways @(S,CLK_OUT,CLK2_OUT,CLK3_OUT,CLK4_OUT)begincase(S)2'd0:CLK<=CLK_OUT;2'd1:CLK<=CLK2_OUT;2'd2:CLK<=CLK3_OUT;2'd3:CLK<=CLK4_OUT;endcaseendinitial begin LED=8'b00000000;endalways @(posedge CLK)beginif(C)//C==1,left shiftingif(RST) LED<=8'b00000001;else if(LED==8'b00000000)LED<=8'b00000001;else LED<=LED<<1;else//C==1,right shiftingif(RST) LED<=8'b10000000;else if(LED==8'b00000000)LED<=8'b10000000;else LED<=LED>>1;endendmoduleIII、用户约束文件 led_shiftingdisplay.vNET "C" LOC = N3;NET "CLK_IN" LOC = B8;NET "LED[0]" LOC = M5;NET "LED[1]" LOC = M11;NET "LED[2]" LOC = P7;NET "LED[3]" LOC = P6;NET "LED[4]" LOC = N5;NET "LED[5]" LOC = N4;NET "LED[6]" LOC = P4;NET "LED[7]" LOC = G1;NET "RST" LOC = A7;NET "S[0]" LOC = P11;NET "S[1]" LOC = L3;# PlanAhead Generated IO constraints NET "C" IOSTANDARD = LVCMOS33;NET "CLK_IN" IOSTANDARD = LVCMOS33;NET "LED[0]" IOSTANDARD = LVCMOS33;NET "LED[1]" IOSTANDARD = LVCMOS33;NET "LED[2]" IOSTANDARD = LVCMOS33;NET "LED[3]" IOSTANDARD = LVCMOS33;NET "LED[4]" IOSTANDARD = LVCMOS33;NET "LED[5]" IOSTANDARD = LVCMOS33;NET "LED[6]" IOSTANDARD = LVCMOS33;NET "LED[7]" IOSTANDARD = LVCMOS33;NET "RST" IOSTANDARD = LVCMOS33;NET "S[0]" IOSTANDARD = LVCMOS33;NET "S[1]" IOSTANDARD = LVCMOS33;IV、程序仿真测试文件 led_shiftingdisplay.vmodule test_ledshiftingdisplay;reg CLK_IN;reg RST;reg [1:0] S;reg C; wire [7:0] LED;led_shiftingdisplay uut (.LED(LED), .CLK_IN(CLK_IN), .RST(RST), .S(S), .C(C));parameter PERIOD = 20; initialbegin CLK_IN = 1'b0; #10; forever #(PERIOD/2) CLK_IN = ~CLK_IN; endinitial beginRST = 0;S = 3;C = 1;endendmodule仿真波形：各个信号仿真波形正常，唯有 LED[7:0]均为高阻态（除最低位外），仿真不成功，不得其解。
