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module prot_eng_tx
#(parameter BASE=0)
(input clk, input reset, input clear,
input set_stb, input [7:0] set_addr, input [31:0] set_data,
input [35:0] datain, input src_rdy_i, output dst_rdy_o,
output [35:0] dataout, output src_rdy_o, input dst_rdy_i);
wire src_rdy_int1, dst_rdy_int1;
wire src_rdy_int2, dst_rdy_int2;
wire [35:0] data_int1, data_int2;
// Shortfifo on input to guarantee no deadlock
fifo_short #(.WIDTH(36)) head_fifo
(.clk(clk),.reset(reset),.clear(clear),
.datain(datain), .src_rdy_i(src_rdy_i), .dst_rdy_o(dst_rdy_o),
.dataout(data_int1), .src_rdy_o(src_rdy_int1), .dst_rdy_i(dst_rdy_int1),
.space(),.occupied() );
// Store header values in a small dual-port (distributed) ram
reg [31:0] header_ram[0:63];
wire [31:0] header_word;
reg [3:0] state;
reg [1:0] port_sel;
always @(posedge clk)
if(set_stb & ((set_addr & 8'hC0) == BASE))
header_ram[set_addr[5:0]] <= set_data;
assign header_word = header_ram[{port_sel[1:0],state[3:0]}];
// Protocol State Machine
reg [15:0] length;
wire [15:0] ip_length = length + 28; // IP HDR + UDP HDR
wire [15:0] udp_length = length + 8; // UDP HDR
reg sof_o;
reg [31:0] prot_data;
always @(posedge clk)
if(reset)
begin
state <= 0;
sof_o <= 0;
end
else
if(src_rdy_int1 & dst_rdy_int2)
case(state)
0 :
begin
port_sel <= data_int1[18:17];
length <= data_int1[15:0];
sof_o <= 1;
if(data_int1[16])
state <= 1;
else
state <= 12;
end
12 :
begin
sof_o <= 0;
if(data_int1[33]) // eof
state <= 0;
end
default :
begin
sof_o <= 0;
state <= state + 1;
end
endcase // case (state)
wire [15:0] ip_checksum;
add_onescomp #(.WIDTH(16)) add_onescomp
(.A(header_word[15:0]),.B(ip_length),.SUM(ip_checksum));
always @*
case(state)
1 : prot_data <= header_word; // ETH, top half ignored
2 : prot_data <= header_word; // ETH
3 : prot_data <= header_word; // ETH
4 : prot_data <= header_word; // ETH
5 : prot_data <= { header_word[31:16], ip_length }; // IP
6 : prot_data <= header_word; // IP
7 : prot_data <= { header_word[31:16], (16'hFFFF ^ ip_checksum) }; // IP
8 : prot_data <= header_word; // IP
9 : prot_data <= header_word; // IP
10: prot_data <= header_word; // UDP
11: prot_data <= { udp_length, header_word[15:0]}; // UDP
default : prot_data <= data_int1[31:0];
endcase // case (state)
assign data_int2 = { data_int1[35:33] & {3{state[3]}}, sof_o, prot_data };
assign dst_rdy_int1 = dst_rdy_int2 & ((state == 0) | (state == 12));
assign src_rdy_int2 = src_rdy_int1 & (state != 0);
// Shortfifo on output to guarantee no deadlock
fifo_short #(.WIDTH(36)) tail_fifo
(.clk(clk),.reset(reset),.clear(clear),
.datain(data_int2), .src_rdy_i(src_rdy_int2), .dst_rdy_o(dst_rdy_int2),
.dataout(dataout), .src_rdy_o(src_rdy_o), .dst_rdy_i(dst_rdy_i),
.space(),.occupied() );
endmodule // prot_eng_tx
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