1 files changed, 77 insertions, 0 deletions
diff --git a/usrp2/simple_gemac/ethtx_realign.v b/usrp2/simple_gemac/ethtx_realign.v
new file mode 100644
index 000000000..be53abf4c
--- /dev/null
+++ b/usrp2/simple_gemac/ethtx_realign.v
@@ -0,0 +1,77 @@
+
+////////////////////////////////////////////////////////////////////////
+// Ethernet TX - Realign
+//
+// - removes a 2-byte pad from the front a fifo36 stream
+// - occupancy is preserved
+//
+
+module ethtx_realign
+   (input clk, input reset, input clear,
+    input [35:0] datain, input src_rdy_i, output dst_rdy_o,
+    output [35:0] dataout, output src_rdy_o, input dst_rdy_i);
+
+   reg [1:0] 	  state;
+   reg [15:0] 	  held;
+   reg [1:0] 	  held_occ;
+   reg 		  held_sof;
+   
+   wire 	  xfer_in = src_rdy_i & dst_rdy_o;
+   wire 	  xfer_out = src_rdy_o & dst_rdy_i;
+
+   wire 	  sof_in = datain[32];
+   wire 	  eof_in = datain[33];
+   wire [1:0] 	  occ_in = datain[35:34];
+   wire 	  occ_low = occ_in[1] ^ occ_in[0]; //occ is 1 or 2
+
+   always @(posedge clk)
+     if(reset | clear)
+       begin
+	  held <= 0;
+	  held_occ <= 0;
+	  held_sof <= 0;
+       end
+     else if(xfer_in)
+       begin
+	  held <= datain[15:0];
+	  held_occ <= occ_in;
+	  held_sof <= sof_in;
+       end
+   
+   localparam RE_IDLE = 0;
+   localparam RE_HELD = 1;
+   localparam RE_DONE = 2;
+
+   always @(posedge clk)
+     if(reset | clear)
+       state <= RE_IDLE;
+     else
+       case(state)
+	 RE_IDLE :
+	   if(xfer_in & eof_in)
+	     state <= RE_DONE;
+	   else if(xfer_in & sof_in)
+	     state <= RE_HELD;
+
+	 RE_HELD :
+	   if(xfer_in & xfer_out & eof_in)
+	     if(occ_low)
+	       state <= RE_IDLE;
+	     else
+	       state <= RE_DONE;
+
+	 RE_DONE :
+	   if(xfer_out)
+	     state <= RE_IDLE;
+	 
+       endcase // case (state)
+
+   wire sof_out = held_sof;
+   wire eof_out = (state == RE_HELD)? (eof_in & occ_low) : (state == RE_DONE);
+   wire [1:0] occ_out = ((state == RE_DONE)? held_occ : occ_in) ^ 2'b10; //(occ + 2)%4
+
+   assign dataout = {occ_out,eof_out,sof_out,held,datain[31:16]};
+   assign src_rdy_o = (state == RE_HELD)? src_rdy_i : (state == RE_DONE);
+   assign dst_rdy_o = (state == RE_HELD)? dst_rdy_i : (state == RE_IDLE);
+
+endmodule // ethtx_realign