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////////////////////////////////////////////////////////////////////////////////

//

// Filename:    enetpackets.v

//

// Project:     OpenArty, an entirely open SoC based upon the Arty platform

//

// Purpose:     To communicate between the Ethernet PHY, and thus to coordinate

//              (and direct/arrange for) the transmission, and receiption, of 

//      packets via the Ethernet interface.

//

//

//      Using this interface requires four registers to be properly configured.

//      These are the receive and transmit control registers, as well as the

//      hardware MAC register(s).

//

//

//      To use the interface, after the system has been alive for a full

//      second, drop the reset line.  Do this by writing to the transmit

//      register a value with zero length, zero command, and the RESET bit as

//      zero.

//

//      This interface is big endian.  Therefore, the most significant byte

//      in each word will be transmitted first.  If the interface references

//      a number of octets less than a multiple of four, the least significant

//      octets in the last word will not be transmitted/were not received.

//

//      To transmit,

//              1. set the source MAC address in the two mac registers.  These

//                      are persistent across packets, so once set (whether for

//                      transmit or receive) they need not be set again.

//              2. Fill the packet buffer with your packet.  In general, the

//                      first 32-bit word must contain the hardware MAC address

//                      of your destination, spilling into the 16-bits of the

//                      next word.  The bottom 16-bits of that second word

//                      must also contain the EtherType (0x0800 for IP,

//                      0x0806 for ARP, etc.)  The third word will begin your

//                      user data.

//              3. Write a 0x4000 plus the number of bytes in your buffer to

//                      the transmit command register.  If your packet is less

//                      than 64 bytes, it will automatically be paddedd to 64

//                      bytes before being sent.

//              4. Once complete, the controller will raise an interrupt

//                      line to note that the interface is idle.

//      OPTIONS:

//              You can turn off the internal insertion of the hardware source

//              MAC by turning the respective bit on in the transmit command

//              register.  If you do this, half of the second word and all the

//              third word must contain the hardware MAC.  The third word must

//              contain the EtherType, both in the top and bottom sixteen bits.

//              The Fourth word will begin user data.

//

//              You can also turn off the automatic insertion of the FCS, or

//              ethernet CRC.  Doing this means that you will need to both 

//              guarantee for yourself that the packet has a minimum of 64

//              bytes in length, and that the last four bytes contain the

//              CRC.

//

//      To Receive: 

//              The receiver is always on.  Receiving is really just a matter

//              of pulling the received packet from the interface, and resetting

//              the interface for the next packet.

//

//              If the VALID bit is set, the receive interface has a valid

//              packet within it.  Write a zero to this bit to reset the

//              interface to accept the next packet.

//

//              If a packet with a CRC error is received, the CRC error bit

//              will be set.  Likewise if a packet has been missed, usually 

//              because the buffer was full when it started, the miss bit

//              will be set.  Finally, if an error occurrs while receiving

//              a packet, the error bit will be set.  These bits may be cleared

//              by writing a one to each of them--something that may be done

//              when clearing the interface for the next packet.

//      OPTIONS:

//              The same options that apply to the transmitter apply to the

//              receiver:

//

//              HWMAC.  If the hardware MAC is turned on, the receiver will

//              only accept packets to either 1) our network address, or 2)

//              a broadcast address.  Further, the first two words will be

//              adjusted to contain the source MAC and the EtherType, so that

//              the user information begins on the third word.  If this feature

//              is turned off, all packets will be received, and the first

//              three words will contain the destination and then source

//              MAC.  The fourth word will contain the EtherType in the lowest,

//              16 bits, meaning user data will begin on the fifth word.

//

//              HWCRC.  If the HWCRC is turned on, the receiver will only

//              detect packets that pass their CRC check.  Further, the packet

//              length (always in octets) will not include the CRC.  However,

//              the CRC will still be left/written to packet memory either way.

//

// Registers:

//      0        Receiver control

//              13'h0   |CRCerr|MISS|ERR|BUSY|VALID |14-bit length (in octets)|

//

//      1       Transmitter control

//              14'h0   |NET_RST|SW-MAC-CHK|SW-CRCn|BUSY/CMD | 14 bit length(in octets)|

//

//      2       // MAC address (high) ??

//      3       // MAC address (low)  ??

//      4       Number of receive packets missed (buffer was full)

//      5       Number of receive packets ending in error

//      6       Number of receive packets with invalid CRCs

//      7       (Number of transmit collisions ??)

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2016, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory, run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

// `define      RX_SYNCHRONOUS_WITH_WB_CLK

`ifdef  RX_SYNCHRONOUS_WITH_WB_CLK

`define RXCLK   i_wb_clk

`else

`define RXCLK   i_net_rx_clk

`endif

// `define      TX_SYNCHRONOUS_WITH_WB_CLK

`ifdef  TX_SYNCHRONOUS_WITH_WB_CLK

`define TXCLK   i_wb_clk

`else

`define TXCLK   i_net_tx_clk

`endif

module  enetpackets(i_wb_clk, i_reset,

        i_wb_cyc, i_wb_stb, i_wb_we, i_wb_addr, i_wb_data, i_wb_sel,

                o_wb_ack, o_wb_stall, o_wb_data,

        //

        o_net_reset_n,

        i_net_rx_clk, i_net_col, i_net_crs, i_net_dv, i_net_rxd, i_net_rxerr,

        i_net_tx_clk, o_net_tx_en, o_net_txd,

        //

        o_rx_int, o_tx_int,

        //

        o_debug

        );

        parameter       MEMORY_ADDRESS_WIDTH = 12; // Log_2 octet width:11..14

        localparam      MAW =((MEMORY_ADDRESS_WIDTH>14)? 14: // width of words

                        ((MEMORY_ADDRESS_WIDTH<11)? 11:MEMORY_ADDRESS_WIDTH))-2;

        input                   i_wb_clk, i_reset;

        //

        input                   i_wb_cyc, i_wb_stb, i_wb_we;

        input   [(MAW+1):0]      i_wb_addr; // 1-bit for ctrl/data, 1 for tx/rx

        input   [31:0]           i_wb_data;

        input   [3:0]            i_wb_sel;

        //

        output  reg             o_wb_ack;

        output  wire            o_wb_stall;

        output  reg     [31:0]   o_wb_data;

        //

        output  reg             o_net_reset_n;

        //

        input                   i_net_rx_clk, i_net_col, i_net_crs, i_net_dv;

        input           [3:0]    i_net_rxd;

        input                   i_net_rxerr;

        //

        input                   i_net_tx_clk;

        output  wire            o_net_tx_en;

        output  wire    [3:0]    o_net_txd;

        //

        output  wire            o_rx_int, o_tx_int;

        //

        output  wire    [31:0]   o_debug;

        reg     wr_ctrl;

        reg     [2:0]    wr_addr;

        reg     [31:0]   wr_data;

        reg     [3:0]    wr_sel;

        always @(posedge i_wb_clk)

        begin

                wr_ctrl<=((i_wb_stb)&&(i_wb_we)&&(i_wb_addr[(MAW+1):MAW] == 2'b00));

                wr_addr <= i_wb_addr[2:0];

                wr_data <= i_wb_data;

                wr_sel  <= i_wb_sel;

        end

        reg     [31:0]   txmem   [0:((1<<MAW)-1)];

        reg     [31:0]   rxmem   [0:((1<<MAW)-1)];

        reg     [(MAW+1):0]      tx_len;

`ifdef  RX_SYNCHRONOUS_WITH_WB_CLK

        wire    rx_broadcast;

        wire    [(MAW+1):0]      rx_len;

`else

        (* ASYNC_REG = "TRUE" *) reg    rx_broadcast;

        (* ASYNC_REG = "TRUE" *) reg    [(MAW+1):0]      rx_len;

`endif

        reg     tx_cmd, tx_cancel;

`ifdef  TX_SYNCHRONOUS_WITH_WB_CLK

        wire    tx_busy, tx_complete;

`else

        reg     tx_busy, tx_complete;

`endif

        reg     config_hw_crc, config_hw_mac, config_hw_ip_check;

        reg     rx_crcerr, rx_err, rx_miss, rx_clear;

`ifdef  RX_SYNCHRONOUS_WITH_WB_CLK

        wire    rx_valid, rx_busy;

`else

        reg     rx_valid, rx_busy;

`endif

        reg     rx_wb_valid, pre_ack, pre_cmd, tx_nzero_cmd;

        reg     [4:0]    caseaddr;

        reg     [31:0]   rx_wb_data, tx_wb_data;

        reg             rx_err_stb, rx_miss_stb, rx_crc_stb;

        reg     [47:0]   hw_mac;

        reg             p_rx_clear;

        reg     [7:0]    clear_pipe;

        initial config_hw_crc = 0;

        initial config_hw_mac = 0;

        initial config_hw_ip_check = 0;

        initial o_net_reset_n = 1'b0;

        initial tx_cmd    = 1'b0;

        initial tx_cancel = 1'b0;

        initial rx_crcerr = 1'b0;

        initial rx_err    = 1'b0;

        initial rx_miss   = 1'b0;

        initial rx_clear  = 1'b0;

        always @(posedge i_wb_clk)

        begin

                // if (i_wb_addr[(MAW+1):MAW] == 2'b10)

                        // Writes to rx memory not allowed here

                if ((i_wb_stb)&&(i_wb_we)&&(i_wb_addr[(MAW+1):MAW] == 2'b11)

                                &&(i_wb_sel[3]))

                        txmem[i_wb_addr[(MAW-1):0]][31:24] <= i_wb_data[31:24];

                if ((i_wb_stb)&&(i_wb_we)&&(i_wb_addr[(MAW+1):MAW] == 2'b11)

                                &&(i_wb_sel[2]))

                        txmem[i_wb_addr[(MAW-1):0]][23:16] <= i_wb_data[23:16];

                if ((i_wb_stb)&&(i_wb_we)&&(i_wb_addr[(MAW+1):MAW] == 2'b11)

                                &&(i_wb_sel[1]))

                        txmem[i_wb_addr[(MAW-1):0]][15:8] <= i_wb_data[15:8];

                if ((i_wb_stb)&&(i_wb_we)&&(i_wb_addr[(MAW+1):MAW] == 2'b11)

                                &&(i_wb_sel[0]))

                        txmem[i_wb_addr[(MAW-1):0]][7:0] <= i_wb_data[7:0];

                // Set the err bits on these conditions (filled out below)

                if (rx_err_stb)

                        rx_err <= 1'b1;

                if (rx_miss_stb)

                        rx_miss <= 1'b1;

                if (rx_crc_stb)

                        rx_crcerr <= 1'b1;

                if ((wr_ctrl)&&(wr_addr==3'b000))

                begin // RX command register

                        rx_crcerr<= (!wr_data[18])&&(!rx_crcerr);

                        rx_err   <= (!wr_data[17])&&(!rx_err);

                        rx_miss  <= (!wr_data[16])&&(!rx_miss);

                        // busy bit cannot be written to

                        rx_clear <= rx_clear || (wr_data[14]);

                        // Length bits are cleared when invalid

                end else if (!rx_valid)

                        rx_clear <= 1'b0;

                clear_pipe <= { clear_pipe[6:0], rx_clear };

                p_rx_clear <= |clear_pipe;

                if ((tx_busy)||(tx_cancel))

                        tx_cmd <= 1'b0;

                if (!tx_busy)

                        tx_cancel <= 1'b0;

                pre_cmd <= 1'b0;

                if ((wr_ctrl)&&(wr_addr==3'b001))

                begin // TX command register

                        // Reset bit must be held down to be valid

                        config_hw_ip_check <= (!wr_data[18]);

                        o_net_reset_n <= (!wr_data[17]);

                        config_hw_mac <= (!wr_data[16]);

                        config_hw_crc <= (!wr_data[15]);

                        pre_cmd <= (wr_data[14]);

                        tx_cancel <= (tx_busy)&&(!wr_data[14]);

//              14'h0   | SW-CRCn |NET-RST|BUSY/CMD | 14 bit length(in octets)|

                        tx_len <= wr_data[(MAW+1):0];

                end

                tx_nzero_cmd <= ((pre_cmd)&&(tx_len != 0));

                if (tx_nzero_cmd)

                        tx_cmd <= 1'b1;

                if (!o_net_reset_n)

                        tx_cancel <= 1'b1;

                if (!o_net_reset_n)

                        tx_cmd <= 1'b0;

                if ((wr_ctrl)&&(wr_addr==3'b010))

                        hw_mac[47:32] <= wr_data[15:0];

                if ((wr_ctrl)&&(wr_addr==3'b011))

                        hw_mac[31:0] <= wr_data[31:0];

        end

        wire    [31:0]   w_tx_ctrl;

        wire    [31:0]   w_rx_ctrl;

        wire    [3:0]    w_maw;

        assign  w_maw = MAW+2; // Number of bits in the packet length field

        assign  w_rx_ctrl = { 4'h0, w_maw, {(24-20){1'b0}},

                        (rx_valid)&&(rx_broadcast)&&(!rx_clear),

                        rx_crcerr, rx_err,

                        rx_miss, rx_busy, (rx_valid)&&(!rx_clear),

                        {(14-MAW-2){1'b0}}, rx_len };

        assign  w_tx_ctrl = { 4'h0, w_maw, {(24-19){1'b0}},

                        !config_hw_ip_check,

                        !o_net_reset_n,!config_hw_mac,

                        !config_hw_crc, tx_busy,

                                {(14-MAW-2){1'b0}}, tx_len };

        reg     [31:0]   counter_rx_miss, counter_rx_err, counter_rx_crc;

        initial counter_rx_miss = 32'h00;

        initial counter_rx_err  = 32'h00;

        initial counter_rx_crc  = 32'h00;

        // Reads from the bus ... always done, regardless of i_wb_we

        always @(posedge i_wb_clk)

        begin

                rx_wb_data  <= rxmem[i_wb_addr[(MAW-1):0]];

                rx_wb_valid <= (i_wb_addr[(MAW-1):0] <= { rx_len[(MAW+1):2] });

                tx_wb_data  <= txmem[i_wb_addr[(MAW-1):0]];

                pre_ack <= i_wb_stb;

                caseaddr <= {i_wb_addr[(MAW+1):MAW], i_wb_addr[2:0] };

                casez(caseaddr)

                5'h00: o_wb_data <= w_rx_ctrl;

                5'h01: o_wb_data <= w_tx_ctrl;

                5'h02: o_wb_data <= {16'h00, hw_mac[47:32] };

                5'h03: o_wb_data <= hw_mac[31:0];

                5'h04: o_wb_data <= counter_rx_miss;

                5'h05: o_wb_data <= counter_rx_err;

                5'h06: o_wb_data <= counter_rx_crc;

                5'h07: o_wb_data <= 32'h00;

                5'b10???: o_wb_data <= (rx_wb_valid)?rx_wb_data:32'h00;

                5'b11???: o_wb_data <= tx_wb_data;

                default: o_wb_data <= 32'h00;

                endcase

                o_wb_ack <= pre_ack;

        end

        /////////////////////////////////////

        //

        //

        //

        // Transmitter code

        //

        //

        //

        /////////////////////////////////////

`ifdef  TX_SYNCHRONOUS_WITH_WB_CLK

        reg     [(MAW+1):0]      n_tx_len;

        wire    n_tx_cmd, n_tx_cancel;

        assign  n_tx_cmd = tx_cmd;

        assign  n_tx_cancel = tx_cancel;

`else

        (* ASYNC_REG = "TRUE" *) reg    [(MAW+1):0]      n_tx_len;

        (* ASYNC_REG = "TRUE" *) reg r_tx_cmd, r_tx_cancel;

        reg     n_tx_cmd, n_tx_cancel;

        always @(posedge `TXCLK)

        begin

                r_tx_cmd    <= tx_cmd;

                r_tx_cancel <= tx_cancel;

                n_tx_cmd    <= r_tx_cmd;

                n_tx_cancel <= r_tx_cancel;

        end

`endif

`ifdef  TX_SYNCHRONOUS_WITH_WB_CLK

        reg     last_tx_clk, tx_clk_stb;

        (* ASYNC_REG = "TRUE" *) reg    r_tx_clk;

        always @(posedge i_wb_clk)

                r_tx_clk <= i_net_tx_clk;

        always @(posedge i_wb_clk)

                last_tx_clk <= r_tx_clk;

        always @(posedge i_wb_clk)

                tx_clk_stb <= (r_tx_clk)&&(!last_tx_clk);

`else

        wire    tx_clk_stb, last_tx_clk;

        assign  tx_clk_stb = 1'b1;

        assign  last_tx_clk= 1'b0;

`endif

        wire    [(MAW+2):0]      rd_tx_addr;

        assign  rd_tx_addr = (n_tx_addr+8);

        reg     [(MAW+2):0]      n_tx_addr;

        reg     [31:0]           n_tx_data, n_next_tx_data;

        reg                     n_tx_complete;

`ifdef  TX_SYNCHRONOUSH_WITH_WB

        reg             n_tx_busy, n_tx_config_hw_mac, n_tx_config_hw_crc;

`else

        (* ASYNC_REG = "TRUE" *) reg    n_tx_busy,

                                        n_tx_config_hw_mac, n_tx_config_hw_crc;

`endif

        (* ASYNC_REG = "TRUE" *) reg r_tx_crs;

        reg     n_tx_crs;

        always @(posedge `TXCLK)

        begin

                r_tx_crs <= i_net_crs;

                n_tx_crs <= r_tx_crs;

        end

        wire    [31:0]   n_remap_tx_data;

        assign  n_remap_tx_data[31:28] = n_next_tx_data[27:24];

        assign  n_remap_tx_data[27:24] = n_next_tx_data[31:28];

        assign  n_remap_tx_data[23:20] = n_next_tx_data[19:16];

        assign  n_remap_tx_data[19:16] = n_next_tx_data[23:20];

        assign  n_remap_tx_data[15:12] = n_next_tx_data[11: 8];

        assign  n_remap_tx_data[11: 8] = n_next_tx_data[15:12];

        assign  n_remap_tx_data[ 7: 4] = n_next_tx_data[ 3: 0];

        assign  n_remap_tx_data[ 3: 0] = n_next_tx_data[ 7: 4];

        reg             r_txd_en;

        reg     [3:0]    r_txd;

        initial r_txd_en = 1'b0;

        initial n_tx_busy  = 1'b0;

        initial n_tx_complete  = 1'b0;

        always @(posedge `TXCLK)

        begin

                if (tx_clk_stb)

                begin

                        // While this operation doesn't strictly need to 

                        // operate *only* if tx_clk_stb is true, by doing so

                        // our code stays compatible with both synchronous

                        // to wishbone and synchronous to tx clk options.

                        n_next_tx_data  <= txmem[(!n_tx_busy)?0:rd_tx_addr[(MAW+2):3]];

                end

                if (n_tx_cancel)

                        n_tx_busy <= 1'b0;

                else if (!n_tx_busy)

                        n_tx_busy <= (n_tx_cmd)&&(!i_net_crs);

                else if (n_tx_addr >= { n_tx_len,1'b0 })

                        n_tx_busy     <= 1'b0;

                if (!n_tx_busy)

                begin

                        n_tx_addr  <= {{(MAW+2){1'b0}},1'b1};

                        n_tx_data <= { n_remap_tx_data[27:0], 4'h0 };

                        if (n_tx_complete)

                                n_tx_complete <= (!n_tx_cmd);

                        r_txd_en <= (!n_tx_complete)&&(n_tx_cmd)&&(!i_net_crs);

                        r_txd  <= n_remap_tx_data[31:28];

                        n_tx_config_hw_mac <= config_hw_mac;

                        n_tx_config_hw_crc <= config_hw_crc;

                        n_tx_len <= tx_len;

                end else if (!r_txd_en)

                        r_txd_en <= (!n_tx_crs);

                else if (tx_clk_stb) begin

                        n_tx_addr <= n_tx_addr + 1'b1;

                        r_txd <= n_tx_data[31:28];

                        if (n_tx_addr[2:0] == 3'h7)

                                n_tx_data <= n_remap_tx_data;

                        else

                                n_tx_data <= { n_tx_data[27:0], 4'h0 };

                        if (n_tx_addr >= { n_tx_len,1'b0 })

                                n_tx_complete <= 1'b1;

                        r_txd_en <= (n_tx_addr < { n_tx_len, 1'b0 });

                end

        end

        wire    n_tx_config_hw_preamble;

        assign  n_tx_config_hw_preamble = 1'b1;

        wire            w_macen, w_paden, w_txcrcen;

        wire    [3:0]    w_macd,  w_padd,  w_txcrcd;

`ifndef TX_BYPASS_HW_MAC

        addemac txmaci(`TXCLK, tx_clk_stb, n_tx_config_hw_mac, n_tx_cancel,

                                hw_mac, r_txd_en, r_txd, w_macen, w_macd);

`else

        assign  w_macen = r_txd_en;

        assign  w_macd  = r_txd;

`endif

`ifndef TX_BYPASS_PADDING

        addepad txpadi(`TXCLK, tx_clk_stb, 1'b1, n_tx_cancel,

                                w_macen, w_macd, w_paden, w_padd);

`else

        assign  w_paden = w_macen;

        assign  w_padd  = w_macd;

`endif

`ifndef TX_BYPASS_HW_CRC

        addecrc txcrci(`TXCLK, tx_clk_stb, n_tx_config_hw_crc, n_tx_cancel,

                                w_paden, w_padd, w_txcrcen, w_txcrcd);

`else

        assign  w_txcrcen = w_macen;

        assign  w_txcrcd  = w_macd;

`endif

        addepreamble txprei(`TXCLK, tx_clk_stb, n_tx_config_hw_preamble, n_tx_cancel,

                                w_txcrcen, w_txcrcd, o_net_tx_en, o_net_txd);

`ifdef  TX_SYNCRONOUS_WITH_WB_CLK

        assign  tx_busy = n_tx_busy;

        assign  tx_complete = n_tx_complete;

`else

        (* ASYNC_REG = "TRUE" *) reg    r_tx_busy, r_tx_complete;

        always @(posedge i_wb_clk)

        begin

                r_tx_busy <= (n_tx_busy || o_net_tx_en || w_txcrcen || w_macen || w_paden);

                tx_busy <= r_tx_busy;

                r_tx_complete <= n_tx_complete;

                tx_busy <= r_tx_busy;

        end

`endif

        /////////////////////////////////////

        //

        //

        //

        // Receiver code

        //

        //

        //

        /////////////////////////////////////

`ifdef  RX_SYNCHRONOUS_WITH_WB_CLK

        reg     last_rx_clk, rx_clk_stb;

        (* ASYNC_REG="TRUE" *) reg r_rx_clk;

        always @(posedge i_wb_clk)

                r_rx_clk <= i_net_rx_clk;

        always @(posedge i_wb_clk)

                last_rx_clk <= r_rx_clk;

        always @(posedge i_wb_clk)

                rx_clk_stb <= (r_rx_clk)&&(!last_rx_clk);

`else

        wire    rx_clk_stb, last_rx_clk;

        assign  rx_clk_stb = 1'b1;

        assign  last_rx_clk = 1'b0;

`endif

`ifdef  RX_SYNCHRONOUS_WITH_WB_CLK

        wire    n_rx_clear;

        reg     n_rx_config_hw_mac, n_rx_config_hw_crc, n_rx_config_ip_check;

        assign  n_rx_clear = rx_clear;

`else

        (* ASYNC_REG = "TRUE" *) reg n_rx_config_hw_mac, n_rx_config_hw_crc,

                        n_rx_config_ip_check;

        (* ASYNC_REG = "TRUE" *) reg r_rx_clear;

        reg     n_rx_clear;

        always @(posedge `RXCLK)

        begin

                r_rx_clear <= (p_rx_clear)||(!o_net_reset_n);

                n_rx_clear <= r_rx_clear;

        end

`endif

        reg             n_rx_net_err;

        wire            w_npre,  w_rxmin,  w_rxcrc,  w_rxmac;

        wire    [3:0]    w_npred, w_rxmind, w_rxcrcd, w_rxmacd;

        wire            w_minerr, w_rxcrcerr, w_macerr, w_broadcast, w_iperr;

`ifndef RX_BYPASS_HW_PREAMBLE

        rxepreambl rxprei(`RXCLK, rx_clk_stb, 1'b1, (n_rx_net_err),

                        i_net_dv, i_net_rxd, w_npre, w_npred);

`else

        assign  w_npre  = i_net_dv;

        assign  w_npred = i_net_rxerr;

`endif

`ifdef  RX_BYPASS_HW_MINLENGTH

        // Insist on a minimum of 64-byte packets

        rxemin  rxmini(`RXCLK, rx_clk_stb, 1'b1, (n_rx_net_err),

                        w_npre, w_npred, w_minerr);

`else

        assign  w_minerr= 1'b0;

`endif

        assign  w_rxmin = w_npre;

        assign  w_rxmind= w_npred;

`ifndef RX_BYPASS_HW_CRC

        rxecrc  rxcrci(`RXCLK, rx_clk_stb, n_rx_config_hw_crc, (n_rx_net_err),

                        w_rxmin, w_rxmind, w_rxcrc, w_rxcrcd, w_rxcrcerr);

`else

        assign  w_rxcrc   = w_rxmin;

        assign  w_rxcrcd  = w_rxmind;

        assign  w_rxcrcerr= 1'b0;

`endif