CPLD一个很奇怪的问题

2019-03-25 08:15发布

用CPLD做编码器的解码，用的是状态机写的485通讯，遇到一个很奇怪的问题，写的状态机如下：
   case(state)
      Idle:
      begin
         over <= 1'b0;
         txd <= 1'b1;
         if(start_fg == 1'b1)
         begin
            state <= Request;
            E_c <= 1'b1;
            start_fg1 <= 1'b1;
         end
      end
      Request:
      begin
         if(i == 8'd10)
            begin
               state <= Wait;
               start_fg1 <= 1'b0;
               E_c <= 1'b0;
               CF_r <= 10'd0;
               txd <= 1'b1;
               i <= 6'd0;
            end
         else
         begin
            txd <= CF[6'd9-i];
            i <= i+1'b1;
         end
      end
   Wait:
      begin
         txd <= 1'b1;
         E_b <= 1'b1;
         if(CF_r[3:0] == 4'b0010)
            begin
                  state <= Receive;
                  i <= 6'd0;
                  CF_r <= (CF_r << 1)|re;
                  i <= 6'd4;
            end
         else
            begin
                  CF_r <= (CF_r << 1)|re;
                  if(i == 4'd14)
                     begin
                     state <= Idle;
                     erro <= 2'd3;
                     end
                  else
                     begin
                        i <= i+1'b1;
                     end
            end
      end
      Receive:
         begin
            if(i < 6'd9)
            begin
               CF_r <= (CF_r << 1)|re;
               i <= i+1'b1;
               end
            else if(i == 6'd9)
               begin
                  if(CF_r == CF)
                     begin
                        CRC_buf <= CRC_buf|{CF_r[8:1],40'd0};
                        CF_r <= (CF_r << 1)|re;
                        i <= i+1'b1;
                     end
                  else
                     begin
                        state <= Idle;
                        i <= 0;
                     erro <= 2'd0;
                     end
               end
            else if(i < 6'd19)
               begin
                  CF_r <= (CF_r << 1)|re;
                  i <= i+1'b1;
               end
            else if(i == 6'd19)
               begin
                  if(CF_r[4] | CF_r[3])
                     begin
                        erro <= 2'd2;
                        i <= i+1'b1;
                     end
                  else
                     begin
                        CRC_buf <= CRC_buf|{CF_r[8:1],32'd0};
                        DATA_TEMP <= (DATA_TEMP >> 1)|{re, 29'd0};
                        i <= i+1'b1;
                     end
               end
               else if(i < 6'd49)
                  begin
                     DATA_TEMP <= (DATA_TEMP >> 1)|{re, 29'd0};
                     i <= i+1'b1;
                  end
               else if(i < 6'd59)
                  begin
                     CF_r <= (CF_r << 1)|re;
                     i <= i+1'b1;
                  end
               else
                  begin
                     DATA_TEMP[23:0] = {DATA_TEMP[28:21],DATA_TEMP[18:11],DATA_TEMP[8:1]};
                     for(i = 6'd0; i < 24; i = i+1'd1)
                     begin
                        CRC_buf[31-i] = DATA_TEMP;
                  end
                  CRC_buf = CRC_buf|CF_r[8:1];
                  for(i = 6'd47; i > 6'd7; i = i-1'b1)
                  begin
                     CRC_buf[47:40] = {CRC_buf[46:40],(CRC_buf[47]^CRC_buf[39])};
                     CRC_buf[39:0] = CRC_buf[38:0]<<1; //shift
                  end
                  if (!CRC_buf[47:40])
                     begin
                        DATA_LAST =DATA; //24'd3;//
                        DATA =DATA_TEMP[23:0];  //24'h01fffd; //
                     end
                  else
                  begin
                        CRC_buf[47:40]=8'd0;
                     DATA=24'hffffff;
                  end
            state <= Idle;
            E_b <= 1'd0;
            i <= 6'd0;
            over <= 1'd1;
         end
      end
   endcase
加了一句如下划线的语句后，状态机不跳了，txd没有输出，看RTL Viewer太复杂了查不过来，有没有哪位有经验的前辈能够指点一下这会是什么原因呢？DATA跟状态机完全没有关系呢。。

[ 本帖最后由 mlovew723 于 2013-11-23 09:37 编辑 ] 此帖出自小平头技术问答

友情提示: 此问题已得到解决，问题已经关闭,关闭后问题禁止继续编辑，回答。