工業(yè)控制現(xiàn)場
很多智能儀表都具備RS-232和RS-485兩種通信接口類型。
RS-232是美國1969年公布的通信協(xié)議，也是工業(yè)控制中應用最廣泛的一種串行接口，采取不平衡傳輸方式。
缺點：傳輸距離短，最大約30米，傳輸速率低，最高20kb/s，共模能力差，抗干擾能力弱，所以RS232只適合本地設備之間的通信。
RS-485是彌補RS232通信距離短，傳輸速率低等不足之處，于1983年提出一種串行數(shù)據(jù)接口標準，RS485采用差分傳輸方式，也叫平衡傳輸，有較高的噪音抑制能力，最大傳輸距離約1200米，最大傳輸速率10Mb/s增加了雙向通信能力，所以RS485是首選的串行接口。
網(wǎng)絡通信協(xié)議
主機和從機之間搭建的是RS-485網(wǎng)絡，硬件是采用RS-485接線，主機呼叫從機地址，從機應答方式通訊。
數(shù)據(jù)幀10位，1位起始位，8個數(shù)據(jù)位，1個停止位，無效驗。波特率：9600；19200；38400。

RS485可以聯(lián)網(wǎng)構成分布式，最多并聯(lián)32臺驅動器和32臺接收器。
RS485設備網(wǎng)想要互相通信，只有通過主設備（PC）中轉才能實現(xiàn)，設備網(wǎng)只容許有一個主設備，其余都是從設備。
RS485電壓范圍-7~+12V
邏輯“1”，—2v-6v
邏輯“0”，—(-2v)-(-6v)

（1）通過RS232/RS485轉換電路將PC機串口RS232信號轉換成RS485信號，對于情況比較復雜的工業(yè)環(huán)境最好是選用防浪涌帶隔離珊的產品。（2）通過PCI多串口卡，可以直接選用輸出信號為RS485類型的擴展卡。

頭文件：uart_tx_top.v

/*************************************************** * Module Name : uart_tx_top * Engineer : 小梅哥 * Target Device : EP4CE10F17C8 * Tool versions : Quartus II 13.0 * Create Date : 2017-3-31 * Revision : v1.0 * Description : 串口發(fā)送頂層設計 **************************************************/module uart_tx_top(Clk, //50M時鐘輸入Rst_n, //系統(tǒng)復位Rs232_Tx, //Rs232輸出信號Rs232_Rx, //RS232數(shù)據(jù)輸入Rs232_Ren,key_in0, //按鍵控制輸入led //數(shù)據(jù)發(fā)送狀態(tài));input Clk;input Rst_n;input key_in0;output Rs232_Tx;input Rs232_Rx;output Rs232_Ren;output led;wire send_en;wire [7:0]data_byte;wire [7:0]data_rx;wire key_flag0;wire key_state0;wire [2:0]baud_set;wire uart_state;assign led = uart_state;assign send_en = key_flag0 & !key_state0;assign Rs232_Ren = uart_state;assign data_byte = 8'b1010_1111;//afassign baud_set = 3'd4; //設置波特率為115200bpsuart_byte_tx uart_byte_tx(.Clk(Clk),.Rst_n(Rst_n),.data_byte(data_byte),.send_en(send_en),.baud_set(baud_set),.Rs232_Tx(Rs232_Tx),.Tx_Done(),.uart_state(uart_state));key_filter key_filter0(.Clk(Clk),.Rst_n(Rst_n),.key_in(key_in0),.key_flag(key_flag0),.key_state(key_state0));/*ISSP ISSP(.probe(data_rx),.source(data_byte));*/uart_byte_rx uart_byte_rx(.Clk(Clk),.Rst_n(Rst_n),.baud_set(baud_set),.Rs232_Rx(Rs232_Rx),.data_byte(data_rx),.Rx_Done(Rx_Done));endmodule

按鍵模塊
key_filter.v

/*************************************************** * Module Name : key_filter * Engineer : 小梅哥 * Target Device : EP4CE10F17C8 * Tool versions : Quartus II 13.0 * Create Date : 2017-3-31 * Revision : v1.0 * Description : 單按鍵消抖設計 **************************************************/module key_filter(Clk, //50M時鐘輸入Rst_n, //模塊復位key_in, //按鍵輸入key_flag, //按鍵標志信號key_state //按鍵狀態(tài)信號);input Clk;input Rst_n;input key_in;output reg key_flag;output reg key_state;localparamIDEL = 4'b0001,FILTER0 = 4'b0010,DOWN = 4'b0100,FILTER1 = 4'b1000;reg [3:0]state;reg [19:0]cnt;reg en_cnt; //使能計數(shù)寄存器//對外部輸入的異步信號進行同步處理reg key_in_sa,key_in_sb;always@(posedge Clk or negedge Rst_n)if(!Rst_n)beginkey_in_sa <= 1'b0;key_in_sb <= 1'b0;endelse beginkey_in_sa <= key_in;key_in_sb <= key_in_sa; endreg key_tmpa,key_tmpb;wire pedge,nedge;reg cnt_full;//計數(shù)滿標志信號//使用D觸發(fā)器存儲兩個相鄰時鐘上升沿時外部輸入信號（已經同步到系統(tǒng)時鐘域中）的電平狀態(tài)always@(posedge Clk or negedge Rst_n)if(!Rst_n)beginkey_tmpa <= 1'b0;key_tmpb <= 1'b0;endelse beginkey_tmpa <= key_in_sb;key_tmpb <= key_tmpa; end//產生跳變沿信號 assign nedge = !key_tmpa & key_tmpb;assign pedge = key_tmpa & (!key_tmpb);always@(posedge Clk or negedge Rst_n)if(!Rst_n)beginen_cnt <= 1'b0;state <= IDEL;key_flag <= 1'b0;key_state <= 1'b1;endelse begincase(state)IDEL :beginkey_flag <= 1'b0;if(nedge)beginstate <= FILTER0;en_cnt <= 1'b1;endelsestate <= IDEL;endFILTER0:if(cnt_full)beginkey_flag <= 1'b1;key_state <= 1'b0;en_cnt <= 1'b0;state <= DOWN;endelse if(pedge)beginstate <= IDEL;en_cnt <= 1'b0;endelsestate <= FILTER0;DOWN:beginkey_flag <= 1'b0;if(pedge)beginstate <= FILTER1;en_cnt <= 1'b1;endelsestate <= DOWN;endFILTER1:if(cnt_full)beginkey_flag <= 1'b1;key_state <= 1'b1;state <= IDEL;endelse if(nedge)beginen_cnt <= 1'b0;state <= DOWN;endelsestate <= FILTER1;default:begin state <= IDEL; en_cnt <= 1'b0; key_flag <= 1'b0;key_state <= 1'b1;endendcase endalways@(posedge Clk or negedge Rst_n)if(!Rst_n)cnt <= 20'd0;else if(en_cnt)cnt <= cnt + 1'b1;elsecnt <= 20'd0;always@(posedge Clk or negedge Rst_n)if(!Rst_n)cnt_full <= 1'b0;else if(cnt == 999_999)cnt_full <= 1'b1;elsecnt_full <= 1'b0; endmodule

單字節(jié)接收模塊
uart_byte_rx.v

/*************************************************** * Module Name : uart_byte_rx * Engineer : 小梅哥 * Target Device : EP4CE10F17C8 * Tool versions : Quartus II 13.0 * Create Date : 2017-3-31 * Revision : v1.0 * Description : 串口接收模塊設計 **************************************************/module uart_byte_rx(Clk, //模塊時鐘50MRst_n, //模塊復位baud_set, //波特率設置Rs232_Rx, //RS232數(shù)據(jù)輸入data_byte, //并行數(shù)據(jù)輸出Rx_Done //一次數(shù)據(jù)接收完成標志);input Clk;input Rst_n;input [2:0]baud_set;input Rs232_Rx;output reg [7:0]data_byte;output reg Rx_Done;reg s0_Rs232_Rx,s1_Rs232_Rx;//同步寄存器reg tmp0_Rs232_Rx,tmp1_Rs232_Rx;//數(shù)據(jù)寄存器reg [15:0]bps_DR;//分頻計數(shù)器計數(shù)最大值reg [15:0]div_cnt;//分頻計數(shù)器reg bps_clk;//reg [7:0]bps_cnt;reg uart_state;reg [2:0] r_data_byte [7:0];//reg [7:0] tmp_data_byte;reg [2:0] START_BIT,STOP_BIT;wire nedege;//同步寄存器，消除亞穩(wěn)態(tài)always@(posedge Clk or negedge Rst_n)if(!Rst_n)begins0_Rs232_Rx <= 1'b0;s1_Rs232_Rx <= 1'b0; endelse begins0_Rs232_Rx <= Rs232_Rx;s1_Rs232_Rx <= s0_Rs232_Rx; end//數(shù)據(jù)寄存器always@(posedge Clk or negedge Rst_n)if(!Rst_n)begintmp0_Rs232_Rx <= 1'b0;tmp1_Rs232_Rx <= 1'b0; endelse begintmp0_Rs232_Rx <= s1_Rs232_Rx;tmp1_Rs232_Rx <= tmp0_Rs232_Rx; endassign nedege = !tmp0_Rs232_Rx & tmp1_Rs232_Rx;always@(posedge Clk or negedge Rst_n)if(!Rst_n)bps_DR <= 16'd324;else begincase(baud_set)0:bps_DR <= 16'd324;1:bps_DR <= 16'd162;2:bps_DR <= 16'd80;3:bps_DR <= 16'd53;4:bps_DR <= 16'd26;default:bps_DR <= 16'd324; endcaseend//counteralways@(posedge Clk or negedge Rst_n)if(!Rst_n)div_cnt <= 16'd0;else if(uart_state)beginif(div_cnt == bps_DR)div_cnt <= 16'd0;elsediv_cnt <= div_cnt + 1'b1;endelsediv_cnt <= 16'd0;// bps_clk genalways@(posedge Clk or negedge Rst_n)if(!Rst_n)bps_clk <= 1'b0;else if(div_cnt == 16'd1)bps_clk <= 1'b1;elsebps_clk <= 1'b0;//bps counteralways@(posedge Clk or negedge Rst_n)if(!Rst_n) bps_cnt <= 8'd0;else if(bps_cnt == 8'd159 | (bps_cnt == 8'd12 && (START_BIT > 2)))bps_cnt <= 8'd0;else if(bps_clk)bps_cnt <= bps_cnt + 1'b1;elsebps_cnt <= bps_cnt;always@(posedge Clk or negedge Rst_n)if(!Rst_n)Rx_Done <= 1'b0;else if(bps_cnt == 8'd159)Rx_Done <= 1'b1;elseRx_Done <= 1'b0;// always@(posedge Clk or negedge Rst_n) // if(!Rst_n) // data_byte <= 8'd0; // else if(bps_cnt == 8'd159) // data_byte <= tmp_data_byte; // else // data_byte <= data_byte;always@(posedge Clk or negedge Rst_n)if(!Rst_n)data_byte <= 8'd0;else if(bps_cnt == 8'd159)begindata_byte[0] <= r_data_byte[0][2];data_byte[1] <= r_data_byte[1][2];data_byte[2] <= r_data_byte[2][2];data_byte[3] <= r_data_byte[3][2];data_byte[4] <= r_data_byte[4][2];data_byte[5] <= r_data_byte[5][2];data_byte[6] <= r_data_byte[6][2];data_byte[7] <= r_data_byte[7][2];end always@(posedge Clk or negedge Rst_n)if(!Rst_n)beginSTART_BIT = 3'd0;r_data_byte[0] <= 3'd0;r_data_byte[1] <= 3'd0;r_data_byte[2] <= 3'd0;r_data_byte[3] <= 3'd0;r_data_byte[4] <= 3'd0;r_data_byte[5] <= 3'd0;r_data_byte[6] <= 3'd0;r_data_byte[7] <= 3'd0;STOP_BIT = 3'd0;endelse if(bps_clk)begincase(bps_cnt)0:beginSTART_BIT = 3'd0;r_data_byte[0] <= 3'd0;r_data_byte[1] <= 3'd0;r_data_byte[2] <= 3'd0;r_data_byte[3] <= 3'd0;r_data_byte[4] <= 3'd0;r_data_byte[5] <= 3'd0;r_data_byte[6] <= 3'd0;r_data_byte[7] <= 3'd0;STOP_BIT = 3'd0; end6,7,8,9,10,11:START_BIT <= START_BIT + s1_Rs232_Rx;22,23,24,25,26,27:r_data_byte[0] <= r_data_byte[0] + s1_Rs232_Rx;38,39,40,41,42,43:r_data_byte[1] <= r_data_byte[1] + s1_Rs232_Rx;54,55,56,57,58,59:r_data_byte[2] <= r_data_byte[2] + s1_Rs232_Rx;70,71,72,73,74,75:r_data_byte[3] <= r_data_byte[3] + s1_Rs232_Rx;86,87,88,89,90,91:r_data_byte[4] <= r_data_byte[4] + s1_Rs232_Rx;102,103,104,105,106,107:r_data_byte[5] <= r_data_byte[5] + s1_Rs232_Rx;118,119,120,121,122,123:r_data_byte[6] <= r_data_byte[6] + s1_Rs232_Rx;134,135,136,137,138,139:r_data_byte[7] <= r_data_byte[7] + s1_Rs232_Rx;150,151,152,153,154,155:STOP_BIT <= STOP_BIT + s1_Rs232_Rx;default:beginSTART_BIT = START_BIT;r_data_byte[0] <= r_data_byte[0];r_data_byte[1] <= r_data_byte[1];r_data_byte[2] <= r_data_byte[2];r_data_byte[3] <= r_data_byte[3];r_data_byte[4] <= r_data_byte[4];r_data_byte[5] <= r_data_byte[5];r_data_byte[6] <= r_data_byte[6];r_data_byte[7] <= r_data_byte[7];STOP_BIT = STOP_BIT; endendcaseendalways@(posedge Clk or negedge Rst_n)if(!Rst_n)uart_state <= 1'b0;else if(nedege)uart_state <= 1'b1;else if(Rx_Done || (bps_cnt == 8'd12 && (START_BIT > 2)))uart_state <= 1'b0;elseuart_state <= uart_state; endmodule

單字節(jié)發(fā)送模塊
uart_byte_tx.v

/*************************************************** * Module Name : uart_byte_tx * Engineer : 小梅哥 * Target Device : EP4CE10F17C8 * Tool versions : Quartus II 13.0 * Create Date : 2017-3-31 * Revision : v1.0 * Description : 串口發(fā)送模塊設計 **************************************************/module uart_byte_tx(Clk, //50M時鐘輸入Rst_n, //模塊復位data_byte, //待傳輸8bit數(shù)據(jù)send_en, //發(fā)送使能baud_set, //波特率設置Rs232_Tx, //Rs232輸出信號Tx_Done, //一次發(fā)送數(shù)據(jù)完成標志uart_state //發(fā)送數(shù)據(jù)狀態(tài) );input Clk;input Rst_n;input [7:0]data_byte;input send_en;input [2:0]baud_set;output reg Rs232_Tx;output reg Tx_Done;output reg uart_state;reg bps_clk; //波特率時鐘reg [15:0]div_cnt;//分頻計數(shù)器reg [15:0]bps_DR;//分頻計數(shù)最大值reg [3:0]bps_cnt;//波特率時鐘計數(shù)器reg [7:0]r_data_byte;localparam START_BIT = 1'b0;localparam STOP_BIT = 1'b1;always@(posedge Clk or negedge Rst_n)if(!Rst_n)uart_state <= 1'b0;else if(send_en)uart_state <= 1'b1;else if(bps_cnt == 4'd11)uart_state <= 1'b0;elseuart_state <= uart_state;always@(posedge Clk or negedge Rst_n)if(!Rst_n)r_data_byte <= 8'd0;else if(send_en)r_data_byte <= data_byte;elser_data_byte <= r_data_byte;always@(posedge Clk or negedge Rst_n)if(!Rst_n)bps_DR <= 16'd5207;else begincase(baud_set)0:bps_DR <= 16'd5207;1:bps_DR <= 16'd2603;2:bps_DR <= 16'd1301;3:bps_DR <= 16'd867;4:bps_DR <= 16'd433;default:bps_DR <= 16'd5207; endcaseend //counteralways@(posedge Clk or negedge Rst_n)if(!Rst_n)div_cnt <= 16'd0;else if(uart_state)beginif(div_cnt == bps_DR)div_cnt <= 16'd0;elsediv_cnt <= div_cnt + 1'b1;endelsediv_cnt <= 16'd0;// bps_clk genalways@(posedge Clk or negedge Rst_n)if(!Rst_n)bps_clk <= 1'b0;else if(div_cnt == 16'd1)bps_clk <= 1'b1;elsebps_clk <= 1'b0;//bps counteralways@(posedge Clk or negedge Rst_n)if(!Rst_n) bps_cnt <= 4'd0;else if(bps_cnt == 4'd11)bps_cnt <= 4'd0;else if(bps_clk)bps_cnt <= bps_cnt + 1'b1;elsebps_cnt <= bps_cnt;always@(posedge Clk or negedge Rst_n)if(!Rst_n)Tx_Done <= 1'b0;else if(bps_cnt == 4'd11)Tx_Done <= 1'b1;elseTx_Done <= 1'b0;always@(posedge Clk or negedge Rst_n)if(!Rst_n)Rs232_Tx <= 1'b1;else begincase(bps_cnt)0:Rs232_Tx <= 1'b1;1:Rs232_Tx <= START_BIT;2:Rs232_Tx <= r_data_byte[0];3:Rs232_Tx <= r_data_byte[1];4:Rs232_Tx <= r_data_byte[2];5:Rs232_Tx <= r_data_byte[3];6:Rs232_Tx <= r_data_byte[4];7:Rs232_Tx <= r_data_byte[5];8:Rs232_Tx <= r_data_byte[6];9:Rs232_Tx <= r_data_byte[7];10:Rs232_Tx <= STOP_BIT;default:Rs232_Tx <= 1'b1;endcaseend endmodule

RS485通信完成

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