// Send an ethernet packet over GMII
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// Send an ethernet packet over GMII
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module gmii_driver
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module gmii_driver
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(output reg [7:0] rxd,
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(output reg [7:0] rxd,
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output reg rx_dv,
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output reg rx_dv,
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output reg rx_clk);
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output reg rx_clk);
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integer startup_skew;
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integer startup_skew;
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reg [7:0] rxbuf [0:2048];
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reg [7:0] rxbuf [0:2048];
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reg [31:0] crc32_result;
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reg [31:0] crc32_result;
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// begin start clock with random skew amount
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// begin start clock with random skew amount
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initial
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initial
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begin
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begin
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startup_skew = {$random} % 200;
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startup_skew = {$random} % 200;
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rx_clk = 0;
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rx_clk = 0;
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rx_dv = 0;
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rx_dv = 0;
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rxd = 0;
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rxd = 0;
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repeat (startup_skew) #0.1;
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repeat (startup_skew) #0.1;
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forever rx_clk = #4 ~rx_clk;
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forever rx_clk = #4 ~rx_clk;
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end
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end
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// Copied from: http://www.mindspring.com/~tcoonan/gencrc.v
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// Copied from: http://www.mindspring.com/~tcoonan/gencrc.v
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//
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//
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// Generate a (DOCSIS) CRC32.
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// Generate a (DOCSIS) CRC32.
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//
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//
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// Uses the GLOBAL variables:
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// Uses the GLOBAL variables:
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//
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//
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// Globals referenced:
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// Globals referenced:
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// parameter CRC32_POLY = 32'h04C11DB7;
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// parameter CRC32_POLY = 32'h04C11DB7;
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// reg [ 7:0] crc32_packet[0:255];
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// reg [ 7:0] crc32_packet[0:255];
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// integer crc32_length;
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// integer crc32_length;
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//
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//
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// Globals modified:
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// Globals modified:
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// reg [31:0] crc32_result;
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// reg [31:0] crc32_result;
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//
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//
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localparam CRC32_POLY = 32'h04C11DB7;
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localparam CRC32_POLY = 32'h04C11DB7;
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task gencrc32;
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task gencrc32;
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input [31:09] crc32_length;
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input [31:09] crc32_length;
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integer cbyte, cbit;
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integer cbyte, cbit;
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reg msb;
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reg msb;
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reg [7:0] current_cbyte;
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reg [7:0] current_cbyte;
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reg [31:0] temp;
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reg [31:0] temp;
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begin
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begin
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crc32_result = 32'hffffffff;
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crc32_result = 32'hffffffff;
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for (cbyte = 0; cbyte < crc32_length; cbyte = cbyte + 1) begin
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for (cbyte = 0; cbyte < crc32_length; cbyte = cbyte + 1) begin
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current_cbyte = rxbuf[cbyte];
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current_cbyte = rxbuf[cbyte];
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for (cbit = 0; cbit < 8; cbit = cbit + 1) begin
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for (cbit = 0; cbit < 8; cbit = cbit + 1) begin
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msb = crc32_result[31];
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msb = crc32_result[31];
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crc32_result = crc32_result << 1;
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crc32_result = crc32_result << 1;
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if (msb != current_cbyte[cbit]) begin
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if (msb != current_cbyte[cbit]) begin
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crc32_result = crc32_result ^ CRC32_POLY;
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crc32_result = crc32_result ^ CRC32_POLY;
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crc32_result[0] = 1;
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crc32_result[0] = 1;
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end
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end
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end
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end
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end
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end
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// Last step is to "mirror" every bit, swap the 4 bytes, and then complement each bit.
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// Last step is to "mirror" every bit, swap the 4 bytes, and then complement each bit.
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//
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//
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// Mirror:
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// Mirror:
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for (cbit = 0; cbit < 32; cbit = cbit + 1)
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for (cbit = 0; cbit < 32; cbit = cbit + 1)
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temp[31-cbit] = crc32_result[cbit];
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temp[31-cbit] = crc32_result[cbit];
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// Swap and Complement:
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// Swap and Complement:
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crc32_result = ~{temp[7:0], temp[15:8], temp[23:16], temp[31:24]};
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crc32_result = ~{temp[7:0], temp[15:8], temp[23:16], temp[31:24]};
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end
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end
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endtask
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endtask
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task print_packet;
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input [31:0] length;
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integer i;
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begin
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for (i=0; i<length; i=i+1)
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begin
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if (i % 16 == 0) $write ("%x: ", i[15:0]);
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$write ("%x ", rxbuf[i]);
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if (i % 16 == 7) $write ("| ");
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if (i % 16 == 15) $write ("\n");
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end
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if (i % 16 != 0) $write ("\n");
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end
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endtask
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task send_packet;
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task send_packet;
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input [47:0] da, sa;
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input [47:0] da, sa;
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input [15:0] length;
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input [15:0] length;
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integer p;
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integer p;
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begin
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begin
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{ rxbuf[0],rxbuf[1],rxbuf[2],rxbuf[3],rxbuf[4],rxbuf[5] } = da;
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{ rxbuf[0],rxbuf[1],rxbuf[2],rxbuf[3],rxbuf[4],rxbuf[5] } = da;
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{ rxbuf[6],rxbuf[7],rxbuf[8],rxbuf[9],rxbuf[10],rxbuf[11] } = sa;
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{ rxbuf[6],rxbuf[7],rxbuf[8],rxbuf[9],rxbuf[10],rxbuf[11] } = sa;
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for (p=12; p<length; p=p+1)
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for (p=12; p<length; p=p+1)
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rxbuf[p] = $random;
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rxbuf[p] = $random;
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gencrc32 (length);
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gencrc32 (length);
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{ rxbuf[length-4], rxbuf[length-3],
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{ rxbuf[length-4], rxbuf[length-3],
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rxbuf[length-2], rxbuf[length-1] } = crc32_result;
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rxbuf[length-2], rxbuf[length-1] } = crc32_result;
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$display ("%m : Sending packet DA=%x SA=%x of length %0d", da, sa, length);
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$display ("%m : Sending packet DA=%x SA=%x of length %0d", da, sa, length);
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print_packet (length);
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repeat (7)
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repeat (7)
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begin
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begin
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@(posedge rx_clk);
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@(posedge rx_clk);
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rx_dv <= #1 1;
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rx_dv <= #1 1;
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rxd <= #1 `GMII_PRE;
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rxd <= #1 `GMII_PRE;
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end
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end
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@(posedge rx_clk);
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@(posedge rx_clk);
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rxd <= #1 `GMII_SFD;
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rxd <= #1 `GMII_SFD;
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p = 0;
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p = 0;
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while (p < length)
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while (p < length)
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begin
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begin
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@(posedge rx_clk);
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@(posedge rx_clk);
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rxd <= #1 rxbuf[p];
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rxd <= #1 rxbuf[p];
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p = p + 1;
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p = p + 1;
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end
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end
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// complete 12B inter frame gap
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// complete 12B inter frame gap
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repeat (12)
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repeat (12)
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begin
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begin
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@(posedge rx_clk);
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@(posedge rx_clk);
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rx_dv <= #1 0;
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rx_dv <= #1 0;
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rxd <= #1 0;
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rxd <= #1 0;
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end
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end
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end
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end
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endtask // send_packet
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endtask // send_packet
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endmodule // gmii_driver
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endmodule // gmii_driver
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