CAN协议FPGA篇

一.引言

CAN（Controller Area Network）总线，即控制器局域网总线，是一种功能丰富的车用总线标准。该协议最初是由德国博世（Bosch）公司在1983年制定的，之后在美国密歇根州底特律举行的汽车工程师协会(SAE) 会议上正式发布推出。1987年，Intel公司推出的首款CAN总线芯片（82526）上市销售。1991年，奔驰汽车发布的第一款基于CAN总线的多路布线系统汽车——W140量产，1993年，国际标准化组织（ISO）发布了CAN标准ISO 11898。后来CAN标准被重新编译分成两个部分：ISO 11898-1涵盖了数据链路层，ISO 11898-2涵盖了高速CAN总线的物理层，所以ISO 11898是针对通信速率为125Kbps~1Mbps的高速通信标准。与此同时，还有另一个标准ISO 11519是针对通信速率为125Kbps以下的低速CAN通信标准，不过ISO 11519后来被此后发布的ISO 11898-3:2006所替代。当然，现在新版的CAN总线芯片支持的通信速率最高波特率也已达5Mbps。

二.CAN总线协议

（1） CAN总线协议图

（2）标准协议数据解析图

（3）拓展协议信息解析图

（4）CAN总线协议传输图

三.FPGA框架设计

（1）控制器设计框图

（2）CAN系统设计框图

四.FPGA代码

（1）整体控制

//连接其他模块
//寄存器模块can_registers i_can_registers (.clk(clk_i),.rst(rst),.cs(cs),.we(we),….）//连接 Bit Timing Logic 模块can_btl i_can_btl (.clk(clk_i),.rst(rst),.rx(rx_i),…）//连接 Bit Streaming Processor 模块can_bsp i_can_bsp(.clk(clk_i),.rst(rst),…）//选择输出 fifo 或者寄存器中的数据模式always @ (extended_mode or addr or reset_mode)beginif (extended_mode & (~reset_mode) & ((addr >= 8'd16) && (addr <= 8'd28)) | (~extended_mode)& ((addr >= 8'd20) && (addr <= 8'd29)))data_out_fifo_selected <= 1'b1;elsedata_out_fifo_selected <= 1'b0;end//输出数据always @ (posedge clk_i)beginif (cs & (~we))beginif (data_out_fifo_selected)data_out <=#Tp data_out_fifo;elsedata_out <=#Tp data_out_regs;endend// 锁存地址always @ (negedge clk_i or posedge rst)beginif (rst)addr_latched <= 8'h0;else if (ale_i)addr_latched <=#Tp port_0_io;end// 产生延迟信号always @ (posedge clk_i or posedge rst)beginif (rst)beginwr_i_q <= 1'b0;rd_i_q <= 1'b0;endelsebeginwr_i_q <=#Tp wr_i;rd_i_q <=#Tp rd_i;endend//组合得到多个信号，如片选、重起等assign cs = ((wr_i & (~wr_i_q)) | (rd_i & (~rd_i_q))) & cs_can_i;assign rst = rst_i;assign we = wr_i;assign addr = addr_latched;assign data_in = port_0_io;assign port_0_io = (cs_can_i & rd_i)? data_out : 8'hz;

（2）寄存器控制模块

always @ (posedge clk)begintx_successful_q <=#Tp tx_successful;overrun_q <=#Tp overrun;transmit_buffer_status_q <=#Tp transmit_buffer_status;info_empty_q <=#Tp info_empty;error_status_q <=#Tp error_status;node_bus_off_q <=#Tp node_bus_off;node_error_passive_q <=#Tp node_error_passive;end…//模式寄存器wire [0:0] mode;wire [4:1] mode_basic;wire [3:1] mode_ext;wire receive_irq_en_basic;wire transmit_irq_en_basic;wire error_irq_en_basic;wire overrun_irq_en_basic;can_register_asyn_syn #(1, 1'h1) MODE_REG0( .data_in(data_in[0]),.data_out(mode[0]),.we(we_mode),.clk(clk),.rst(rst),.rst_sync(set_reset_mode));can_register_asyn #(4, 0) MODE_REG_BASIC( .data_in(data_in[4:1]),.data_out(mode_basic[4:1]),.we(we_mode),.clk(clk),.rst(rst));can_register_asyn #(3, 0) MODE_REG_EXT( .data_in(data_in[3:1]),.data_out(mode_ext[3:1]),.we(we_mode & reset_mode),.clk(clk),.rst(rst));//命令寄存器wire [4:0] command;can_register_asyn_syn #(1, 1'h0) COMMAND_REG0( .data_in(data_in[0]),.data_out(command[0]),.we(we_command),.clk(clk),.rst(rst),.rst_sync(tx_request & sample_point));can_register_asyn_syn #(1, 1'h0) COMMAND_REG1( .data_in(data_in[1]),.data_out(command[1]),.we(we_command),.clk(clk),.rst(rst),.rst_sync(abort_tx & ~transmitting));can_register_asyn_syn #(2, 2'h0) COMMAND_REG( .data_in(data_in[3:2]),.data_out(command[3:2]),.we(we_command),.clk(clk),.rst(rst),.rst_sync(|command[3:2]));can_register_asyn_syn #(1, 1'h0) COMMAND_REG4( .data_in(data_in[4]),.data_out(command[4]),.we(we_command),.clk(clk),.rst(rst),.rst_sync(tx_successful & (~tx_successful_q) | abort_tx));assign self_rx_request = command[4] & (~command[0]);assign clear_data_overrun = command[3];assign release_buffer = command[2];assign abort_tx = command[1] & (~command[0]) & (~command[4]);assign tx_request = command[0] | command[4];always @ (posedge clk or posedge rst)beginif (rst)single_shot_transmission <= 1'b0;else if (we_command & data_in[1] & (data_in[1] | data_in[4]))single_shot_transmission <=#Tp 1'b1;else if (tx_successful & (~tx_successful_q))single_shot_transmission <=#Tp 1'b0;end//状态寄存器wire [7:0] status;assign status[7] = node_bus_off;assign status[6] = error_status;assign status[5] = transmit_status;assign status[4] = receive_status;assign status[3] = transmission_complete;assign status[2] = transmit_buffer_status;assign status[1] = overrun_status;assign status[0] = receive_buffer_status;always @ (posedge clk or posedge rst)beginif (rst)transmission_complete <= 1'b1;else if (tx_successful & (~tx_successful_q) | abort_tx)transmission_complete <=#Tp 1'b1;else if (tx_request)transmission_complete <=#Tp 1'b0;endalways @ (posedge clk or posedge rst)beginif (rst)transmit_buffer_status <= 1'b1;else if (tx_request)transmit_buffer_status <=#Tp 1'b0;else if (~need_to_tx)transmit_buffer_status <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)overrun_status <= 1'b0;else if (overrun & (~overrun_q))overrun_status <=#Tp 1'b1;else if (clear_data_overrun)overrun_status <=#Tp 1'b0;endalways @ (posedge clk or posedge rst)beginif (rst)receive_buffer_status <= 1'b0;else if (release_buffer)receive_buffer_status <=#Tp 1'b0;else if (~info_empty)receive_buffer_status <=#Tp 1'b1;end//总线时序寄存器 1wire [7:0] bus_timing_0;can_register #(8) BUS_TIMING_0_REG( .data_in(data_in),.data_out(bus_timing_0),.we(we_bus_timing_0),.clk(clk));assign baud_r_presc = bus_timing_0[5:0];assign sync_jump_width = bus_timing_0[7:6];//总线时序寄存器 2wire [7:0] bus_timing_1;can_register #(8) BUS_TIMING_1_REG( .data_in(data_in),.data_out(bus_timing_1),.we(we_bus_timing_1),.clk(clk));assign time_segment1 = bus_timing_1[3:0];assign time_segment2 = bus_timing_1[6:4];assign triple_sampling = bus_timing_1[7];//错误提示寄存器can_register_asyn #(8, 96) ERROR_WARNING_REG( .data_in(data_in),.data_out(error_warning_limit),.we(we_error_warning_limit),.clk(clk),.rst(rst));//时钟分频寄存器wire [7:0] clock_divider;wire clock_off;wire [2:0] cd;reg [2:0] clkout_div;reg [2:0] clkout_cnt;reg clkout_tmp;//reg clkout;can_register #(1) CLOCK_DIVIDER_REG_7( .data_in(data_in[7]),.data_out(clock_divider[7]),.we(we_clock_divider_hi),.clk(clk));assign clock_divider[6:4] = 3'h0;can_register #(1) CLOCK_DIVIDER_REG_3( .data_in(data_in[3]),.data_out(clock_divider[3]),.we(we_clock_divider_hi),.clk(clk));can_register #(3) CLOCK_DIVIDER_REG_LOW( .data_in(data_in[2:0]),.data_out(clock_divider[2:0]),.we(we_clock_divider_low),.clk(clk));assign extended_mode = clock_divider[7];assign clock_off = clock_divider[3];assign cd[2:0] = clock_divider[2:0];always @ (cd)begincase (cd) // synopsys_full_case synopsys_paralel_case3'b000 : clkout_div <= 0;3'b001 : clkout_div <= 1;3'b010 : clkout_div <= 2;3'b011 : clkout_div <= 3;3'b100 : clkout_div <= 4;3'b101 : clkout_div <= 5;3'b110 : clkout_div <= 6;3'b111 : clkout_div <= 0;endcaseendalways @ (posedge clk or posedge rst)beginif (rst)clkout_cnt <= 3'h0;else if (clkout_cnt == clkout_div)clkout_cnt <=#Tp 3'h0;elseclkout_cnt <= clkout_cnt + 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)clkout_tmp <= 1'b0;else if (clkout_cnt == clkout_div)clkout_tmp <=#Tp ~clkout_tmp;endalways @ (cd or clkout_tmp or clock_off)beginif (clock_off)clkout <=#Tp 1'b1;elseclkout <=#Tp clkout_tmp;endassign clkout = clock_off ? 1'b1 : ((&cd)? clk : clkout_tmp);//从寄存器中读数据always @ ( addr or read or extended_mode or mode or bus_timing_0 or bus_timing_1 or clock_divideroracceptance_code_0 or acceptance_code_1 or acceptance_code_2 or acceptance_code_3oracceptance_mask_0 or acceptance_mask_1 or acceptance_mask_2 or acceptance_mask_3orreset_mode or tx_data_0 or tx_data_1 or tx_data_2 or tx_data_3 or tx_data_4 ortx_data_5 or tx_data_6 or tx_data_7 or tx_data_8 or tx_data_9 or status orerror_warning_limit or rx_err_cnt or tx_err_cnt or irq_en_ext or irq_reg ormode_ext orarbitration_lost_capture or rx_message_counter or mode_basic orerror_capture_code)beginif(read) // readbeginif (extended_mode) // EXTENDED mode (Different register map depends on mode)begincase(addr)8'd0 : data_out_tmp <= {4'b0000, mode_ext[3:1], mode[0]};8'd1 : data_out_tmp <= 8'h0;8'd2 : data_out_tmp <= status;8'd3 : data_out_tmp <= irq_reg;8'd4 : data_out_tmp <= irq_en_ext;8'd6 : data_out_tmp <= bus_timing_0;8'd7 : data_out_tmp <= bus_timing_1;8'd11 : data_out_tmp <= {3'h0, arbitration_lost_capture[4:0]};8'd12 : data_out_tmp <= error_capture_code;8'd13 : data_out_tmp <= error_warning_limit;8'd14 : data_out_tmp <= rx_err_cnt;8'd15 : data_out_tmp <= tx_err_cnt;8'd16 : data_out_tmp <= acceptance_code_0;8'd17 : data_out_tmp <= acceptance_code_1;8'd18 : data_out_tmp <= acceptance_code_2;8'd19 : data_out_tmp <= acceptance_code_3;8'd20 : data_out_tmp <= acceptance_mask_0;8'd21 : data_out_tmp <= acceptance_mask_1;8'd22 : data_out_tmp <= acceptance_mask_2;8'd23 : data_out_tmp <= acceptance_mask_3;8'd24 : data_out_tmp <= 8'h0;8'd25 : data_out_tmp <= 8'h0;8'd26 : data_out_tmp <= 8'h0;8'd27 : data_out_tmp <= 8'h0;8'd28 : data_out_tmp <= 8'h0;8'd29 : data_out_tmp <= {1'b0, rx_message_counter};8'd31 : data_out_tmp <= clock_divider;default: data_out_tmp <= 8'h0;endcaseendelse // BASIC modebegincase(addr)8'd0 : data_out_tmp <= {3'b001, mode_basic[4:1], mode[0]};8'd1 : data_out_tmp <= 8'hff;8'd2 : data_out_tmp <= status;8'd3 : data_out_tmp <= {4'hf, irq_reg[3:0]};8'd4 : data_out_tmp <= reset_mode? acceptance_code_0 : 8'hff;8'd5 : data_out_tmp <= reset_mode? acceptance_mask_0 : 8'hff;8'd6 : data_out_tmp <= reset_mode? bus_timing_0 : 8'hff;8'd7 : data_out_tmp <= reset_mode? bus_timing_1 : 8'hff;8'd10 : data_out_tmp <= reset_mode? 8'hff : tx_data_0;8'd11 : data_out_tmp <= reset_mode? 8'hff : tx_data_1;8'd12 : data_out_tmp <= reset_mode? 8'hff : tx_data_2;8'd13 : data_out_tmp <= reset_mode? 8'hff : tx_data_3;8'd14 : data_out_tmp <= reset_mode? 8'hff : tx_data_4;8'd15 : data_out_tmp <= reset_mode? 8'hff : tx_data_5;8'd16 : data_out_tmp <= reset_mode? 8'hff : tx_data_6;8'd17 : data_out_tmp <= reset_mode? 8'hff : tx_data_7;8'd18 : data_out_tmp <= reset_mode? 8'hff : tx_data_8;8'd19 : data_out_tmp <= reset_mode? 8'hff : tx_data_9;8'd31 : data_out_tmp <= clock_divider;default: data_out_tmp <= 8'h0;endcaseendendelsedata_out_tmp <= 8'h0;endalways @ (posedge clk or posedge rst)beginif (rst)data_out <= 0;else if (read)data_out <=#Tp data_out_tmp;end

（3）时序逻辑模块

//计数器always @ (posedge clk or posedge rst)beginif (rst)clk_cnt <= 0;else if (clk_cnt == (preset_cnt-1))clk_cnt <=#Tp 0;elseclk_cnt <=#Tp clk_cnt + 1;end//产生定义波特率的一般使能信号always @ (posedge clk or posedge rst)beginif (rst)clk_en <= 1'b0;else if (clk_cnt == (preset_cnt-1))clk_en <=#Tp 1'b1;elseclk_en <=#Tp 1'b0;end//改变状态assign go_sync = clk_en & (seg2 & (~hard_sync) & (~resync) & ((quant_cnt == time_segment2)));assign go_seg1 = clk_en & (sync | hard_sync | (resync & seg2 & sync_window) | (resync_latched& sync_window));assign go_seg2 = clk_en & (seg1 & (~hard_sync) & (quant_cnt == (time_segment1 + delay)));//当探测到 SJW 字段的沿时，同步请求被锁存并被执行always @ (posedge clk or posedge rst)beginif (rst)resync_latched <= 1'b0;else if (resync & seg2 & (~sync_window))resync_latched <=#Tp 1'b1;else if (go_seg1)resync_latched <= 1'b0;end//同步的平台或片断always @ (posedge clk or posedge rst)beginif (rst)sync <= 0;else if (go_sync)sync <=#Tp 1'b1;else if (go_seg1)sync <=#Tp 1'b0;endassign tx_point = go_sync;//片断 seg1always @ (posedge clk or posedge rst)beginif (rst)seg1 <= 1;else if (go_seg1)seg1 <=#Tp 1'b1;else if (go_seg2)seg1 <=#Tp 1'b0;end//片断 seg2always @ (posedge clk or posedge rst)beginif (rst)seg2 <= 0;else if (go_seg2)seg2 <=#Tp 1'b1;else if (go_sync | go_seg1)seg2 <=#Tp 1'b0;end//Quant 计数器always @ (posedge clk or posedge rst)beginif (rst)quant_cnt <= 0;else if (go_sync | go_seg1 | go_seg2)quant_cnt <=#Tp 0;else if (clk_en)quant_cnt <=#Tp quant_cnt + 1'b1;end//当探测到后沿时，片断 seg1 被延时beginif (rst)delay <= 0;else if (clk_en & resync & seg1)delay <=#Tp (quant_cnt > sync_jump_width)? (sync_jump_width + 1) : (quant_cnt + 1);else if (go_sync | go_seg1)delay <=#Tp 0;end//如果沿出现在这个窗口中，相位的错误将得到完全的补偿assign sync_window = ((time_segment2 - quant_cnt) < ( sync_jump_width + 1));//数据采样always @ (posedge clk or posedge rst)beginif (rst)sample <= 2'b11;else if (clk_en)sample <= {sample[0], rx};end//获得使能后，采样完成always @ (posedge clk or posedge rst)beginif (rst)beginsampled_bit <= 1;sampled_bit_q <= 1;sample_point <= 0;endelse if (clk_en & (~hard_sync))beginif (seg1 & (quant_cnt == (time_segment1 + delay)))beginsample_point <=#Tp 1;sampled_bit_q <=#Tp sampled_bit;if (triple_sampling)sampled_bit <=#Tp (sample[0] & sample[1]) | ( sample[0] & rx) | (sample[1] & rx);elsesampled_bit <=#Tp rx;endendelsesample_point <=#Tp 0;end//阻塞同步always @ (posedge clk or posedge rst)beginif (rst)sync_blocked <=#Tp 1'b0;else if (clk_en)beginif (hard_sync | resync)sync_blocked <=#Tp 1'b1;else if (seg2 & quant_cnt == time_segment2)sync_blocked <=#Tp 1'b0;endend//阻塞重同步直到收到开始信号/* Blocking resynchronization until reception starts (needed because after reset mode exitswe are waiting forend-of-frame and interframe. No resynchronization is needed meanwhile). */always @ (posedge clk or posedge rst)beginif (rst)resync_blocked <=#Tp 1'b1;else if (reset_mode)resync_blocked <=#Tp 1'b1;else if (hard_sync)resync_blocked <=#Tp 1'b0;end

（4）位数据流处理器模块

//各个数据收发的起始状态
//接收数据的 idle 状态always @ (posedge clk or posedge rst)beginif (rst)rx_idle <= 1'b0;else if (reset_mode | go_rx_id1 | error_frame)rx_idle <=#Tp 1'b0;else if (go_rx_idle)rx_idle <=#Tp 1'b1;end// 接收数据的 id1 状态always @ (posedge clk or posedge rst)beginif (rst)rx_id1 <= 1'b0;else if (reset_mode | go_rx_rtr1 | error_frame)rx_id1 <=#Tp 1'b0;else if (go_rx_id1)rx_id1 <=#Tp 1'b1;end//接收数据的 rtr1 状态always @ (posedge clk or posedge rst)beginif (rst)rx_rtr1 <= 1'b0;else if (reset_mode | go_rx_ide | error_frame)rx_rtr1 <=#Tp 1'b0;else if (go_rx_rtr1)rx_rtr1 <=#Tp 1'b1;end//接收数据的 ide 状态always @ (posedge clk or posedge rst)beginif (rst)rx_ide <= 1'b0;else if (reset_mode | go_rx_r0 | go_rx_id2 | error_frame)rx_ide <=#Tp 1'b0;else if (go_rx_ide)rx_ide <=#Tp 1'b1;end//接收数据的 id2 状态always @ (posedge clk or posedge rst)beginif (rst)rx_id2 <= 1'b0;else if (reset_mode | go_rx_rtr2 | error_frame)rx_id2 <=#Tp 1'b0;else if (go_rx_id2)rx_id2 <=#Tp 1'b1;end//接收数据的 rtr2 状态always @ (posedge clk or posedge rst)beginif (rst)rx_rtr2 <= 1'b0;else if (reset_mode | go_rx_r1 | error_frame)rx_rtr2 <=#Tp 1'b0;else if (go_rx_rtr2)rx_rtr2 <=#Tp 1'b1;end//接收数据的 r0 状态always @ (posedge clk or posedge rst)beginif (rst)rx_r1 <= 1'b0;else if (reset_mode | go_rx_r0 | error_frame)rx_r1 <=#Tp 1'b0;else if (go_rx_r1)rx_r1 <=#Tp 1'b1;end//接收数据的 r0 状态always @ (posedge clk or posedge rst)beginif (rst)rx_r0 <= 1'b0;else if (reset_mode | go_rx_dlc | error_frame)rx_r0 <=#Tp 1'b0;else if (go_rx_r0)rx_r0 <=#Tp 1'b1;end//接收数据的 dlc 状态always @ (posedge clk or posedge rst)beginif (rst)rx_dlc <= 1'b0;else if (reset_mode | go_rx_data | go_rx_crc | error_frame)rx_dlc <=#Tp 1'b0;else if (go_rx_dlc)rx_dlc <=#Tp 1'b1;end//接收数据状态always @ (posedge clk or posedge rst)beginif (rst)rx_data <= 1'b0;else if (reset_mode | go_rx_crc | error_frame)rx_data <=#Tp 1'b0;else if (go_rx_data)rx_data <=#Tp 1'b1;end// 接收数据的 crc 状态always @ (posedge clk or posedge rst)beginif (rst)rx_crc <= 1'b0;else if (reset_mode | go_rx_crc_lim | error_frame)rx_crc <=#Tp 1'b0;else if (go_rx_crc)rx_crc <=#Tp 1'b1;end//接收数据 crc 分隔符状态always @ (posedge clk or posedge rst)beginif (rst)rx_crc_lim <= 1'b0;else if (reset_mode | go_rx_ack | error_frame)rx_crc_lim <=#Tp 1'b0;else if (go_rx_crc_lim)rx_crc_lim <=#Tp 1'b1;end//接收数据的应答状态always @ (posedge clk or posedge rst)beginif (rst)rx_ack <= 1'b0;else if (reset_mode | go_rx_ack_lim | error_frame)rx_ack <=#Tp 1'b0;else if (go_rx_ack)rx_ack <=#Tp 1'b1;end//接收数据分隔符状态always @ (posedge clk or posedge rst)beginif (rst)rx_ack_lim <= 1'b0;else if (reset_mode | go_rx_eof | error_frame)rx_ack_lim <=#Tp 1'b0;else if (go_rx_ack_lim)rx_ack_lim <=#Tp 1'b1;end//接收数据的帧尾状态always @ (posedge clk or posedge rst)beginif (rst)rx_eof <= 1'b0;else if (go_rx_inter | error_frame | go_overload_frame)rx_eof <=#Tp 1'b0;else if (go_rx_eof)rx_eof <=#Tp 1'b1;end//帧间空间状态always @ (posedge clk or posedge rst)beginif (rst)rx_inter <= 1'b0;else if (reset_mode | go_rx_idle | go_rx_id1 | go_overload_frame | go_error_frame)rx_inter <=#Tp 1'b0;else if (go_rx_inter)rx_inter <=#Tp 1'b1;end// ID 寄存器always @ (posedge clk or posedge rst)beginif (rst)id <= 0;else if (sample_point & (rx_id1 | rx_id2) & (~bit_de_stuff))id <=#Tp {id[27:0], sampled_bit};end// rtr1 位always @ (posedge clk or posedge rst)beginif (rst)rtr1 <= 0;else if (sample_point & rx_rtr1 & (~bit_de_stuff))rtr1 <=#Tp sampled_bit;end// rtr2 位always @ (posedge clk or posedge rst)beginif (rst)rtr2 <= 0;else if (sample_point & rx_rtr2 & (~bit_de_stuff))rtr2 <=#Tp sampled_bit;end// ide 位always @ (posedge clk or posedge rst)beginif (rst)ide <= 0;else if (sample_point & rx_ide & (~bit_de_stuff))ide <=#Tp sampled_bit;end// 获得数据长度always @ (posedge clk or posedge rst)beginif (rst)data_len <= 0;else if (sample_point & rx_dlc & (~bit_de_stuff))data_len <=#Tp {data_len[2:0], sampled_bit};end// 获得数据always @ (posedge clk or posedge rst)beginif (rst)tmp_data <= 0;else if (sample_point & rx_data & (~bit_de_stuff))tmp_data <=#Tp {tmp_data[6:0], sampled_bit};endalways @ (posedge clk or posedge rst)beginif (rst)write_data_to_tmp_fifo <= 0;else if (sample_point & rx_data & (~bit_de_stuff) & (&bit_cnt[2:0]))write_data_to_tmp_fifo <=#Tp 1'b1;elsewrite_data_to_tmp_fifo <=#Tp 0;endalways @ (posedge clk or posedge rst)beginif (rst)byte_cnt <= 0;else if (write_data_to_tmp_fifo)byte_cnt <=#Tp byte_cnt + 1;else if (reset_mode | (sample_point & go_rx_crc_lim))byte_cnt <=#Tp 0;endalways @ (posedge clk)beginif (write_data_to_tmp_fifo)tmp_fifo[byte_cnt] <=#Tp tmp_data;end// CRC 校验数据always @ (posedge clk or posedge rst)beginif (rst)crc_in <= 0;else if (sample_point & rx_crc & (~bit_de_stuff))crc_in <=#Tp {crc_in[13:0], sampled_bit};end//计数器always @ (posedge clk or posedge rst)beginif (rst)bit_cnt <= 0;else if (go_rx_id1 | go_rx_id2 | go_rx_dlc | go_rx_data | go_rx_crc |go_rx_ack | go_rx_eof | go_rx_inter | go_error_frame | go_overload_frame)bit_cnt <=#Tp 0;else if (sample_point & (~bit_de_stuff))bit_cnt <=#Tp bit_cnt + 1'b1;end//帧尾计数器always @ (posedge clk or posedge rst)beginif (rst)eof_cnt <= 0;else if (sample_point)beginif (reset_mode | go_rx_inter | go_error_frame | go_overload_frame)eof_cnt <=#Tp 0;else if (rx_eof)eof_cnt <=#Tp eof_cnt + 1'b1;endend// 使能位填充always @ (posedge clk or posedge rst)beginif (rst)bit_stuff_cnt_en <= 1'b0;else if (bit_de_stuff_set)bit_stuff_cnt_en <=#Tp 1'b1;else if (bit_de_stuff_reset)bit_stuff_cnt_en <=#Tp 1'b0;end//位填充计数器always @ (posedge clk or posedge rst)beginif (rst)bit_stuff_cnt <= 1;else if (bit_de_stuff_reset)bit_stuff_cnt <=#Tp 1;else if (sample_point & bit_stuff_cnt_en)beginif (bit_stuff_cnt == 5)bit_stuff_cnt <=#Tp 1;else if (sampled_bit == sampled_bit_q)bit_stuff_cnt <=#Tp bit_stuff_cnt + 1'b1;elsebit_stuff_cnt <=#Tp 1;endend// 发送数据的使能位填充always @ (posedge clk or posedge rst)beginif (rst)bit_stuff_cnt_tx_en <= 1'b0;else if (bit_de_stuff_set & transmitting)bit_stuff_cnt_tx_en <=#Tp 1'b1;else if (bit_de_stuff_reset)bit_stuff_cnt_tx_en <=#Tp 1'b0;end//发送数据的位填充计数always @ (posedge clk or posedge rst)beginif (rst)bit_stuff_cnt_tx <= 1;else if (bit_de_stuff_reset)bit_stuff_cnt_tx <=#Tp 1;else if (tx_point_q & bit_stuff_cnt_en)beginif (bit_stuff_cnt_tx == 5)bit_stuff_cnt_tx <=#Tp 1;else if (tx == tx_q)bit_stuff_cnt_tx <=#Tp bit_stuff_cnt_tx + 1'b1;elsebit_stuff_cnt_tx <=#Tp 1;endendassign bit_de_stuff = bit_stuff_cnt == 5;assign bit_de_stuff_tx = bit_stuff_cnt_tx == 5;//位填充错误assign stuff_err = sample_point & bit_stuff_cnt_en & bit_de_stuff & (sampled_bit ==sampled_bit_q);//产生延迟信号always @ (posedge clk)beginreset_mode_q <=#Tp reset_mode;node_bus_off_q <=#Tp node_bus_off;endalways @ (posedge clk or posedge rst)beginif (rst)crc_enable <= 1'b0;else if (go_crc_enable)crc_enable <=#Tp 1'b1;else if (reset_mode | rst_crc_enable)crc_enable <=#Tp 1'b0;end//CRC 校验错误always @ (posedge clk or posedge rst)beginif (rst)crc_err <= 1'b0;else if (go_rx_ack)crc_err <=#Tp crc_in != calculated_crc;else if (reset_mode | error_frame_ended)crc_err <=#Tp 1'b0;end// 一般错误的条件assign form_err = sample_point & ( ((~bit_de_stuff) & rx_ide & sampled_bit & (~rtr1)) |(rx_crc_lim & (~sampled_bit)) | (rx_ack_lim & (~sampled_bit)) | ((eof_cnt < 6) & rx_eof &(~sampled_bit) & (~tx_state) ) | (& rx_eof & (~sampled_bit) & tx_state));always @ (posedge clk or posedge rst)beginif (rst)ack_err_latched <= 1'b0;else if (reset_mode | error_frame_ended | go_overload_frame)ack_err_latched <=#Tp 1'b0;else if (ack_err)ack_err_latched <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)bit_err_latched <= 1'b0;else if (reset_mode | error_frame_ended | go_overload_frame)bit_err_latched <=#Tp 1'b0;else if (bit_err)bit_err_latched <=#Tp 1'b1;end//规则 5assign rule5 = (~node_error_passive) & bit_err & (error_frame & (error_cnt1 < 7) |overload_frame & (overload_cnt1 < 7) );//规则 3always @ (posedge clk or posedge rst)beginif (rst)rule3_exc1_1 <= 1'b0;else if (reset_mode | error_flag_over | rule3_exc1_2)rule3_exc1_1 <=#Tp 1'b0;else if (transmitter & node_error_passive & ack_err)rule3_exc1_1 <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)rule3_exc1_2 <= 1'b0;else if (reset_mode | error_flag_over)rule3_exc1_2 <=#Tp 1'b0;else if (rule3_exc1_1)rule3_exc1_2 <=#Tp 1'b1;else if ((error_cnt1 < 7) & sample_point & (~sampled_bit))rule3_exc1_2 <=#Tp 1'b0;endalways @ (posedge clk or posedge rst)beginif (rst)rule3_exc2 <= 1'b0;else if (reset_mode | error_flag_over)rule3_exc2 <=#Tp 1'b0;else if (transmitter & stuff_err & arbitration_field & sample_point & tx & (~sampled_bit))rule3_exc2 <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)stuff_err_latched <= 1'b0;else if (reset_mode | error_frame_ended | go_overload_frame)stuff_err_latched <=#Tp 1'b0;else if (stuff_err)stuff_err_latched <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)form_err_latched <= 1'b0;else if (reset_mode | error_frame_ended | go_overload_frame)form_err_latched <=#Tp 1'b0;else if (form_err)form_err_latched <=#Tp 1'b1;end//接收数据的 CRC 校验
can_crc i_can_crc_rx(.clk(clk),.data(sampled_bit),.enable(crc_enable & sample_point & (~bit_de_stuff)),.initialize(go_crc_enable),.crc(calculated_crc));assign no_byte0 = rtr1 | (data_len<1);
assign no_byte1 = rtr1 | (data_len<2);// 接收数据 FIFO 的写使能always @ (posedge clk or posedge rst)beginif (rst)wr_fifo <= 1'b0;else if (reset_wr_fifo)wr_fifo <=#Tp 1'b0;else if (go_rx_inter & id_ok & (~error_frame_ended) & ((~tx_state) | self_rx_request))wr_fifo <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)header_cnt <= 0;else if (reset_wr_fifo)header_cnt <=#Tp 0;else if (wr_fifo & storing_header)header_cnt <=#Tp header_cnt + 1;end//数据计数器always @ (posedge clk or posedge rst)beginif (rst)data_cnt <= 0;else if (reset_wr_fifo)data_cnt <=#Tp 0;else if (wr_fifo)data_cnt <=#Tp data_cnt + 1;end// 数据的合成并保存到 FIFO 中always @ (extended_mode or ide or data_cnt or header_cnt or header_len orstoring_header or id or rtr1 or rtr2 or data_len ortmp_fifo[0] or tmp_fifo[2] or tmp_fifo[4] or tmp_fifo[6] ortmp_fifo[1] or tmp_fifo[3] or tmp_fifo[5] or tmp_fifo[7])beginif (storing_header)beginif (extended_mode) // extended modebeginif (ide) // extended formatbegincase (header_cnt) // synthesis parallel_case3'h0 : data_for_fifo <= {1'b1, rtr2, 2'h0, data_len};3'h1 : data_for_fifo <= id[28:21];3'h2 : data_for_fifo <= id[20:13];3'h3 : data_for_fifo <= id[12:5];3'h4 : data_for_fifo <= {id[4:0], 3'h0};default: data_for_fifo <= 0;endcaseendelse // standard formatbegincase (header_cnt) // synthesis parallel_case3'h0 : data_for_fifo <= {1'b0, rtr1, 2'h0, data_len};3'h1 : data_for_fifo <= id[10:3];3'h2 : data_for_fifo <= {id[2:0], 5'h0};default: data_for_fifo <= 0;endcaseendendelse // normal modebegincase (header_cnt) // synthesis parallel_case3'h0 : data_for_fifo <= id[10:3];3'h1 : data_for_fifo <= {id[2:0], rtr1, data_len};default: data_for_fifo <= 0;endcaseendendelsedata_for_fifo <= tmp_fifo[data_cnt-header_len];end// 传输错误帧always @ (posedge clk or posedge rst)beginif (rst)error_frame <= 1'b0;else if (reset_mode | error_frame_ended | go_overload_frame)error_frame <=#Tp 1'b0;else if (go_error_frame)error_frame <=#Tp 1'b1;endalways @ (posedge clk)beginif (sample_point)error_frame_q <=#Tp error_frame;endalways @ (posedge clk or posedge rst)beginif (rst)error_cnt1 <= 1'b0;else if (reset_mode | error_frame_ended | go_error_frame | go_overload_frame)error_cnt1 <=#Tp 1'b0;else if (error_frame & tx_point & (error_cnt1 < 7))error_cnt1 <=#Tp error_cnt1 + 1'b1;endassign error_flag_over = ((~node_error_passive) & sample_point & (error_cnt1 == 7) |node_error_passive & sample_point & (passive_cnt == 5)) & (~enable_error_cnt2);always @ (posedge clk or posedge rst)beginif (rst)error_flag_over_blocked <= 1'b0;else if (reset_mode | error_frame_ended | go_error_frame | go_overload_frame)error_flag_over_blocked <=#Tp 1'b0;else if (error_flag_over)error_flag_over_blocked <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)enable_error_cnt2 <= 1'b0;else if (reset_mode | error_frame_ended | go_error_frame | go_overload_frame)enable_error_cnt2 <=#Tp 1'b0;else if (error_frame & (error_flag_over & sampled_bit))enable_error_cnt2 <=#Tp 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)error_cnt2 <= 0;else if (reset_mode | error_frame_ended | go_error_frame | go_overload_frame)error_cnt2 <=#Tp 0;else if (enable_error_cnt2 & tx_point)error_cnt2 <=#Tp error_cnt2 + 1'b1;endalways @ (posedge clk or posedge rst)beginif (rst)delayed_dominant_cnt <= 0;else if (reset_mode | enable_error_cnt2 | go_error_frame | enable_overload_cnt2 |go_overload_frame)delayed_dominant_cnt <=#Tp 0;else if (sample_point & (~sampled_bit) & ((error_cnt1 == 7) | (overload_cnt1 == 7)))delayed_dominant_cnt <=#Tp delayed_dominant_cnt + 1'b1;end//被动计数always @ (posedge clk or posedge rst)beginif (rst)passive_cnt <= 0;else if (reset_mode | error_frame_ended | go_error_frame | go_overload_frame)passive_cnt <=#Tp 0;else if (sample_point & (passive_cnt < 5))beginif (error_frame_q & (~enable_error_cnt2) & (sampled_bit == sampled_bit_q))passive_cnt <=#Tp passive_cnt + 1'b1;elsepassive_cnt <=#Tp 0;endend// 传输超载帧
always @ (posedge clk or posedge rst)
begin
if (rst)
overload_frame <= 1'b0;
else if (reset_mode | overload_frame_ended | go_error_frame)
overload_frame <=#Tp 1'b0;
else if (go_overload_frame)
overload_frame <=#Tp 1'b1;
end
always @ (posedge clk or posedge rst)
begin
if (rst)
overload_cnt1 <= 1'b0;
else if (reset_mode | overload_frame_ended | go_error_frame | go_overload_frame)
overload_cnt1 <=#Tp 1'b0;
else if (overload_frame & tx_point & (overload_cnt1 < 7))
overload_cnt1 <=#Tp overload_cnt1 + 1'b1;
end
assign overload_flag_over = sample_point & (overload_cnt1 == 7) & (~enable_overload_cnt2);
always @ (posedge clk or posedge rst)
begin
if (rst)
enable_overload_cnt2 <= 1'b0;
else if (reset_mode | overload_frame_ended | go_error_frame | go_overload_frame)
enable_overload_cnt2 <=#Tp 1'b0;
else if (overload_frame & (overload_flag_over & sampled_bit))
enable_overload_cnt2 <=#Tp 1'b1;
end
always @ (posedge clk or posedge rst)
begin
if (rst)
overload_cnt2 <= 0;
else if (reset_mode | overload_frame_ended | go_error_frame | go_overload_frame)
overload_cnt2 <=#Tp 0;
else if (enable_overload_cnt2 & tx_point)
overload_cnt2 <=#Tp overload_cnt2 + 1'b1;
end
always @ (posedge clk or posedge rst)
begin
if (rst)
overload_frame_blocked <= 0;
else if (reset_mode | go_error_frame | go_rx_id1)
overload_frame_blocked <=#Tp 0;
else if (go_overload_frame & overload_frame) // This is a second sequential
overload
overload_frame_blocked <=#Tp 1'b1;
end
assign send_ack = (~tx_state) & rx_ack & (~err) & (~listen_only_mode);
always @ (posedge clk or posedge rst)
begin
if (rst)
tx <= 1'b1;
else if (reset_mode) // Reset
tx <=#Tp 1'b1;
else if (tx_point)
begin
if (tx_state) // 传输报文
tx <=#Tp ((~bit_de_stuff_tx) & tx_bit) | (bit_de_stuff_tx & (~tx_q));
else if (send_ack) // 应答
tx <=#Tp 1'b0;
else if (overload_frame) //传输超载帧
begin
if (overload_cnt1 < 6)
tx <=#Tp 1'b0;
else
tx <=#Tp 1'b1;
end
else if (error_frame) // 传输错误帧
begin
if (error_cnt1 < 6)
begin
if (node_error_passive)
tx <=#Tp 1'b1;
else
tx <=#Tp 1'b0;
end
else
tx <=#Tp 1'b1;
end
else
tx <=#Tp 1'b1;
end
end
always @ (posedge clk)
begin
if (tx_point)
tx_q <=#Tp tx & (~go_early_tx_latched);
end
//延迟发送数据
always @ (posedge clk)
begin
tx_point_q <=#Tp tx_point;
end

（5）CRC校验模块

assign crc_next = data ^ crc[14];assign crc_tmp = {crc[13:0], 1'b0};//CRC 校验always @ (posedge clk)beginif(initialize)crc <= #Tp 0;else if (enable)beginif (crc_next)crc <= #Tp crc_tmp ^ 15'h4599;elsecrc <= #Tp crc_tmp;endend

（6）FIFO模块

assign write_length_info = (~wr) & wr_q;//延迟写信号always @ (posedge clk or posedge rst)beginif (rst)wr_q <= 0;else if (reset_mode)wr_q <=#Tp 0;elsewr_q <=#Tp wr;end// 数据长度计数器always @ (posedge clk or posedge rst)beginif (rst)len_cnt <= 0;else if (reset_mode | write_length_info)len_cnt <=#Tp 1'b0;else if (wr & (~fifo_full))len_cnt <=#Tp len_cnt + 1'b1;end// 写信息指针always @ (posedge clk or posedge rst)beginif (rst)wr_info_pointer <= 0;else if (reset_mode)wr_info_pointer <=#Tp 0;else if (write_length_info & (~info_full))wr_info_pointer <=#Tp wr_info_pointer + 1'b1;end//读信息指针always @ (posedge clk or posedge rst)beginif (rst)rd_info_pointer <= 0;else if (reset_mode)rd_info_pointer <=#Tp 0;else if (release_buffer & (~fifo_empty))rd_info_pointer <=#Tp rd_info_pointer + 1'b1;end// 读指针always @ (posedge clk or posedge rst)beginif (rst)rd_pointer <= 0;else if (release_buffer & (~fifo_empty))rd_pointer <=#Tp rd_pointer + length_info;else if (reset_mode)rd_pointer <=#Tp 0;end// 写指针always @ (posedge clk or posedge rst)beginif (rst)wr_pointer <= 0;else if (wr & (~fifo_full))wr_pointer <=#Tp wr_pointer + 1'b1;else if (reset_mode)wr_pointer <=#Tp 0;end//锁存always @ (posedge clk or posedge rst)beginif (rst)latch_overrun <= 0;else if (reset_mode | write_length_info)latch_overrun <=#Tp 0;else if (wr & fifo_full)latch_overrun <=#Tp 1'b1;end//统计在 FIFO 中的数据always @ (posedge clk or posedge rst)beginif (rst)fifo_cnt <= 0;else if (wr & (~release_buffer) & (~fifo_full))fifo_cnt <=#Tp fifo_cnt + 1'b1;else if ((~wr) & release_buffer & (~fifo_empty))fifo_cnt <=#Tp fifo_cnt - length_info;else if (wr & release_buffer & (~fifo_full) & (~fifo_empty))fifo_cnt <=#Tp fifo_cnt - length_info + 1'b1;else if (reset_mode)fifo_cnt <=#Tp 0;endassign fifo_full = fifo_cnt == 64;assign fifo_empty = fifo_cnt == 0;//统计在 length_fifo 和 overrun_info fifo 中的数据always @ (posedge clk or posedge rst)beginif (rst)info_cnt <= 0;else if (write_length_info ^ release_buffer)beginif (release_buffer & (~info_empty))info_cnt <=#Tp info_cnt - 1'b1;else if (write_length_info & (~info_full))info_cnt <=#Tp info_cnt + 1'b1;endendassign info_full = info_cnt == 64;assign info_empty = info_cnt == 0;//选择用来读数据的 FIFO 的地址always @ (extended_mode or rd_pointer or addr)beginif (extended_mode) // extended modebeginread_address <= rd_pointer + (addr - 8'd16);endelse // normal modebeginread_address <= rd_pointer + (addr - 8'd20);endendalways @ (posedge clk)beginif (wr & (~fifo_full))fifo[wr_pointer] <=#Tp data_in;end//从 FIFO 中读数据assign data_out = fifo[read_address];//写到 length_fifoalways @ (posedge clk)beginif (write_length_info & (~info_full))length_fifo[wr_info_pointer] <=#Tp len_cnt;end// 读 length_fifo 中的数据assign length_info = length_fifo[rd_info_pointer];// overrun_infoalways @ (posedge clk)beginif (write_length_info & (~info_full))overrun_info[wr_info_pointer] <=#Tp latch_overrun | (wr & fifo_full);end// 读取 overrunassign overrun = overrun_info[rd_info_pointer]