barebones udp support. Compiles, but untested.

1 files changed, 119 insertions, 0 deletions

diff --git a/udp/prot_eng_tx.v b/udp/prot_eng_tx.v
new file mode 100644
index 000000000..9031011f7
--- /dev/null
+++ b/udp/prot_eng_tx.v
@@ -0,0 +1,119 @@
+
+// The input FIFO contents should be 16 bits wide
+//   The first word is 1 for fast path (accelerated protocol)
+//                     0 for software implemented protocol
+//   The second word is the number of bytes in the packet, 
+//         and must be valid even if we are in slow path mode
+//            Odd means the last word is half full
+//   Flags[1:0] is {eop, sop}
+//   Protocol word format is:
+//             19   Last Header Line
+//             18   IP Header Checksum XOR
+//             17   IP Length Here
+//             16   UDP Length Here
+//           15:0   data word to be sent
+
+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 [18:0] datain, input src_rdy_i, output dst_rdy_o,
+    output [18:0] dataout, output src_rdy_o, input dst_rdy_i);
+
+   wire [2:0] flags_i = datain[18:16];
+   reg [15:0] dataout_int;
+   reg fast_path, sof_o;
+   
+   wire [2:0] flags_o 	 = {flags_i[2], flags_i[1], sof_o};  // OCC, EOF, SOF
+
+   assign dataout 	 = {flags_o[2:0], dataout_int[15:0]};
+
+   reg [4:0] state;
+   wire do_payload 	 = (state == 31);
+   
+   assign dst_rdy_o 	 = dst_rdy_i & (do_payload | (state==0) | (state==1) | (state==30));
+   assign src_rdy_o 	 = src_rdy_i & ~((state==0) | (state==1) | (state==30));
+   
+   localparam HDR_WIDTH  = 16 + 4;  // 16 bits plus flags
+   localparam HDR_LEN 	 = 32;      // Up to 64 bytes of protocol
+   
+   // Store header values in a small dual-port (distributed) ram
+   reg [HDR_WIDTH-1:0] header_ram[0:HDR_LEN-1];
+   wire [HDR_WIDTH-1:0] header_word;
+   
+   always @(posedge clk)
+     if(set_stb & ((set_addr & 8'hE0) == BASE))
+       header_ram[set_addr[4:0]] <= set_data;
+
+   assign header_word = header_ram[state];
+
+   wire last_hdr_line  = header_word[19];
+   wire ip_chk 	       = header_word[18];
+   wire ip_len 	       = header_word[17];
+   wire udp_len        = header_word[16];
+   
+   // 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
+
+   always @(posedge clk)
+     if(reset)
+       begin
+	  state     <= 0;
+	  fast_path <= 0;
+	  sof_o   <= 0;
+       end
+     else
+       if(src_rdy_i & dst_rdy_i)
+	 case(state)
+	   0 :
+	     begin
+		fast_path <= datain[0];
+		state <= 1;
+	     end
+	   1 :
+	     begin
+		length 	<= datain[15:0];
+		sof_o <= 1;
+		if(fast_path)
+		  state <= 2;
+		else
+		  state <= 30;  // Skip 1 word for alignment
+	     end
+	   30 :
+	     state <= 31;
+	   31 :
+	     begin
+		sof_o <= 0;
+		if(flags_i[1]) // eop
+		  state <= 0;
+	     end
+	   default :
+	     begin
+		sof_o 	<= 0;
+		if(~last_hdr_line)
+		  state <= state + 1;
+		else
+		  state <= 31;
+	     end
+	 endcase // case (state)
+
+   wire [15:0] checksum;
+   add_onescomp #(.WIDTH(16)) add_onescomp 
+     (.A(header_word[15:0]),.B(ip_length),.SUM(checksum));
+
+   always @*
+     if(ip_chk)
+       //dataout_int 	<= header_word[15:0] ^ ip_length;
+       dataout_int 	<= 16'hFFFF ^ checksum;
+     else if(ip_len)
+       dataout_int 	<= ip_length;
+     else if(udp_len)
+       dataout_int 	<= udp_length;
+     else if(do_payload)
+       dataout_int 	<= datain[15:0];
+     else
+       dataout_int 	<= header_word[15:0];
+   
+endmodule // prot_eng_tx