写了一个状态机，按照列进行依次扫描，最后状态机发现只有一列（即设置的初始状态列）有正常输出，其余三列没有输出。状态机对4列状态是无条件转移，即在1k的时钟上升沿依次序跳转的下一列扫描状态。利用tb文件扫描正常，但是实物始终只有一列的输出。（ps：col为output，row为input）谢谢各位！
//两段式状态机
always@(posedge clk_1kHz ) begin
if(!rst_n) state <= 3'd1; //状态机进入的初始状态，从第一列开扫
else state <= nextstate;
end
//通过组合逻辑判断按键输出
always@(state or row) begin
case (state)
1:begin
col = 4'b0001;
case(row)
4'b0001: begin code = 4'b0000; valid = 1; SEG = 8'b1111_1100; end
4'b0010: begin code = 4'b0100; valid = 1; SEG = 8'b0110_0110; end
4'b0100: begin code = 4'b1000; valid = 1; SEG = 8'b1111_1110; end
4'b1000: begin code = 4'b1100; valid = 1; SEG = 8'b1001_1100; end
default: begin code = 4'b1111; valid = 0; SEG = 8'b0000_0000; end
endcase
if(valid) nextstate = 3'd1; //如果是有效输入继续停留在该状态，否则扫描下一列
else nextstate = 3'd2;
end
2:begin
col = 4'b0010;
case(row)
4'b0001: begin code = 4'b0001; valid = 1; SEG = 8'b0110_0000; end
4'b0010: begin code = 4'b0101; valid = 1; SEG = 8'b1011_0110; end
4'b0100: begin code = 4'b1001; valid = 1; SEG = 8'b1111_0110; end
4'b1000: begin code = 4'b1101; valid = 1; SEG = 8'b0111_1010; end
default: begin code = 4'b1111; valid = 0; SEG = 8'b0000_0000; end
endcase
if(valid) nextstate = 3'd2;
else nextstate = 3'd3;
end
3:begin
col = 4'b0100;
case(row)
4'b0001: begin code = 4'b0010; valid = 1; SEG = 8'b1101_1010; end
4'b0010: begin code = 4'b0110; valid = 1; SEG = 8'b1011_1110; end
4'b0100: begin code = 4'b1010; valid = 1; SEG = 8'b1110_1110; end
4'b1000: begin code = 4'b1110; valid = 1; SEG = 8'b1001_1110; end
default: begin code = 4'b1111; valid = 0; SEG = 8'b0000_0000; end
endcase
if(valid) nextstate = 3'd3;
else nextstate = 3'd4;
end
4:begin
col = 4'b1000;
case(row)
4'b0001: begin code = 4'b0011; valid = 1; SEG = 8'b1111_0010; end
4'b0010: begin code = 4'b0111; valid = 1; SEG = 8'b1110_0000; end
4'b0100: begin code = 4'b1011; valid = 1; SEG = 8'b0011_1110; end
4'b1000: begin code = 4'b1111; valid = 1; SEG = 8'b1000_1110; end
default: begin code = 4'b1111; valid = 0; SEG = 8'b0000_0000; end
endcase
if(valid) nextstate = 3'd4;
else nextstate = 3'd1;
end
default: begin col = 4'b0100; valid = 0; code = 4'b1111 ; nextstate = 3'd3; SEG = 8'b0000_0000; end //无效状态数码管不显示
endcase
end