Merge FPGA repository back into UHD repository

The FPGA codebase was removed from the UHD repository in 2014 to reduce
the size of the repository. However, over the last half-decade, the
split between the repositories has proven more burdensome than it has
been helpful. By merging the FPGA code back, it will be possible to
create atomic commits that touch both FPGA and UHD codebases. Continuous
integration testing is also simplified by merging the repositories,
because it was previously difficult to automatically derive the correct
UHD branch when testing a feature branch on the FPGA repository.

This commit also updates the license files and paths therein.

We are therefore merging the repositories again. Future development for
FPGA code will happen in the same repository as the UHD host code and
MPM code.

== Original Codebase and Rebasing ==

The original FPGA repository will be hosted for the foreseeable future
at its original local location: https://github.com/EttusResearch/fpga/

It can be used for bisecting, reference, and a more detailed history.

The final commit from said repository to be merged here is
05003794e2da61cabf64dd278c45685a7abad7ec. This commit is tagged as
v4.0.0.0-pre-uhd-merge.

If you have changes in the FPGA repository that you want to rebase onto
the UHD repository, simply run the following commands:

- Create a directory to store patches (this should be an empty
  directory):

    mkdir ~/patches

- Now make sure that your FPGA codebase is based on the same state as
  the code that was merged:

    cd src/fpga # Or wherever your FPGA code is stored
    git rebase v4.0.0.0-pre-uhd-merge

  Note: The rebase command may look slightly different depending on what
  exactly you're trying to rebase.

- Create a patch set for your changes versus v4.0.0.0-pre-uhd-merge:

    git format-patch v4.0.0.0-pre-uhd-merge -o ~/patches

  Note: Make sure that only patches are stored in your output directory.
  It should otherwise be empty. Make sure that you picked the correct
  range of commits, and only commits you wanted to rebase were exported
  as patch files.

- Go to the UHD repository and apply the patches:

    cd src/uhd # Or wherever your UHD repository is stored
    git am --directory fpga ~/patches/*
    rm -rf ~/patches # This is for cleanup

== Contributors ==

The following people have contributed mainly to these files (this list
is not complete):

Co-authored-by: Alex Williams <alex.williams@ni.com>
Co-authored-by: Andrej Rode <andrej.rode@ettus.com>
Co-authored-by: Ashish Chaudhari <ashish@ettus.com>
Co-authored-by: Ben Hilburn <ben.hilburn@ettus.com>
Co-authored-by: Ciro Nishiguchi <ciro.nishiguchi@ni.com>
Co-authored-by: Daniel Jepson <daniel.jepson@ni.com>
Co-authored-by: Derek Kozel <derek.kozel@ettus.com>
Co-authored-by: EJ Kreinar <ej@he360.com>
Co-authored-by: Humberto Jimenez <humberto.jimenez@ni.com>
Co-authored-by: Ian Buckley <ian.buckley@gmail.com>
Co-authored-by: Jörg Hofrichter <joerg.hofrichter@ni.com>
Co-authored-by: Jon Kiser <jon.kiser@ni.com>
Co-authored-by: Josh Blum <josh@joshknows.com>
Co-authored-by: Jonathon Pendlum <jonathan.pendlum@ettus.com>
Co-authored-by: Martin Braun <martin.braun@ettus.com>
Co-authored-by: Matt Ettus <matt@ettus.com>
Co-authored-by: Michael West <michael.west@ettus.com>
Co-authored-by: Moritz Fischer <moritz.fischer@ettus.com>
Co-authored-by: Nick Foster <nick@ettus.com>
Co-authored-by: Nicolas Cuervo <nicolas.cuervo@ettus.com>
Co-authored-by: Paul Butler <paul.butler@ni.com>
Co-authored-by: Paul David <paul.david@ettus.com>
Co-authored-by: Ryan Marlow <ryan.marlow@ettus.com>
Co-authored-by: Sugandha Gupta <sugandha.gupta@ettus.com>
Co-authored-by: Sylvain Munaut <tnt@246tNt.com>
Co-authored-by: Trung Tran <trung.tran@ettus.com>
Co-authored-by: Vidush Vishwanath <vidush.vishwanath@ettus.com>
Co-authored-by: Wade Fife <wade.fife@ettus.com>

7 files changed, 1072 insertions, 0 deletions

diff --git a/fpga/usrp2/serdes/Makefile.srcs b/fpga/usrp2/serdes/Makefile.srcs
new file mode 100644
index 000000000..bade46ad1
--- /dev/null
+++ b/fpga/usrp2/serdes/Makefile.srcs
@@ -0,0 +1,14 @@
+#
+# Copyright 2010 Ettus Research LLC
+#
+
+##################################################
+# SERDES Sources
+##################################################
+SERDES_SRCS = $(abspath $(addprefix $(BASE_DIR)/../serdes/, \
+serdes.v \
+serdes_fc_rx.v \
+serdes_fc_tx.v \
+serdes_rx.v \
+serdes_tx.v \
+))
diff --git a/fpga/usrp2/serdes/serdes.v b/fpga/usrp2/serdes/serdes.v
new file mode 100644
index 000000000..edbc46419
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes.v
@@ -0,0 +1,80 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+// SERDES TX and RX along with all flow control logic
+
+module serdes
+  #(parameter TXFIFOSIZE = 9,
+    parameter RXFIFOSIZE = 9)
+    (input clk, input rst,
+     // TX side
+     output ser_tx_clk, output [15:0] ser_t, output ser_tklsb, output ser_tkmsb,
+     input [31:0] rd_dat_i, input [3:0] rd_flags_i, output rd_ready_o, input rd_ready_i,
+     // RX side
+     input ser_rx_clk, input [15:0] ser_r, input ser_rklsb, input ser_rkmsb,
+     output [31:0] wr_dat_o, output [3:0] wr_flags_o, output wr_ready_o, input wr_ready_i,
+
+     output [15:0] tx_occupied, output tx_full, output tx_empty,
+     output [15:0] rx_occupied, output rx_full, output rx_empty,
+
+     output serdes_link_up,
+     
+     output [31:0] debug0, 
+     output [31:0] debug1);
+
+   wire [15:0] fifo_space;
+   wire        xon_rcvd, xoff_rcvd, inhibit_tx, send_xon, send_xoff, sent;
+   wire [31:0] debug_rx, debug_tx;
+
+   serdes_tx #(.FIFOSIZE(TXFIFOSIZE)) serdes_tx
+     (.clk(clk),.rst(rst),
+      .ser_tx_clk(ser_tx_clk),.ser_t(ser_t),.ser_tklsb(ser_tklsb),.ser_tkmsb(ser_tkmsb),
+      .rd_dat_i(rd_dat_i),.rd_flags_i(rd_flags_i),.rd_ready_o(rd_ready_o),.rd_ready_i(rd_ready_i),
+      .inhibit_tx(inhibit_tx), .send_xon(send_xon), .send_xoff(send_xoff), .sent(sent),
+      .fifo_occupied(tx_occupied),.fifo_full(tx_full),.fifo_empty(tx_empty),
+      .debug(debug_tx) );
+   
+   serdes_rx #(.FIFOSIZE(RXFIFOSIZE)) serdes_rx
+     (.clk(clk),.rst(rst),
+      .ser_rx_clk(ser_rx_clk),.ser_r(ser_r),.ser_rklsb(ser_rklsb),.ser_rkmsb(ser_rkmsb),
+      .wr_dat_o(wr_dat_o),.wr_flags_o(wr_flags_o),.wr_ready_o(wr_ready_o),.wr_ready_i(wr_ready_i),
+      .fifo_space(fifo_space), .xon_rcvd(xon_rcvd), .xoff_rcvd(xoff_rcvd),
+      .fifo_occupied(rx_occupied),.fifo_full(rx_full),.fifo_empty(rx_empty),
+      .serdes_link_up(serdes_link_up), .debug(debug_rx) );
+
+   serdes_fc_tx serdes_fc_tx
+     (.clk(clk),.rst(rst),
+      .xon_rcvd(xon_rcvd),.xoff_rcvd(xoff_rcvd),.inhibit_tx(inhibit_tx) );
+
+   serdes_fc_rx #(.LWMARK(32),.HWMARK(128)) serdes_fc_rx
+     (.clk(clk),.rst(rst),
+      .fifo_space(fifo_space),.send_xon(send_xon),.send_xoff(send_xoff),.sent(sent) );
+
+   //assign      debug = { fifo_space, send_xon, send_xoff, debug_rx[13:0] };
+   //assign      debug = debug_rx;
+
+   assign      debug0 = { { 2'b00, rd_ready_o, rd_ready_i, rd_flags_i[3:0]},
+			  { debug_tx[5:4] /* full,empty */ , inhibit_tx, send_xon, send_xoff, sent, ser_tkmsb, ser_tklsb},
+			  { ser_t[15:8] },
+			  { ser_t[7:0] } };
+   
+   assign      debug1 = { { debug_rx[7:0] }, /*  odd,xfer_active,sop_i,eop_i,error_i,state[2:0] */
+			  { wr_flags_o[1:0], wr_ready_i, wr_ready_o,  xon_rcvd, xoff_rcvd, ser_rkmsb, ser_rklsb },
+			  { ser_r[15:8] },
+			  { ser_r[7:0] } };
+endmodule // serdes
diff --git a/fpga/usrp2/serdes/serdes_fc_rx.v b/fpga/usrp2/serdes/serdes_fc_rx.v
new file mode 100644
index 000000000..9ea32cf8d
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes_fc_rx.v
@@ -0,0 +1,79 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+
+module serdes_fc_rx
+  #(parameter LWMARK = 64,
+    parameter HWMARK = 320)
+    (input clk, input rst,
+     input [15:0] fifo_space, 
+     output reg send_xon,
+     output reg send_xoff,
+     input sent);
+    
+   reg [15:0] 	  countdown;
+   reg 		  send_xon_int, send_xoff_int;
+   
+   always @(posedge clk)
+     if(rst)
+       begin
+	  send_xon_int <= 0;
+	  send_xoff_int <= 0;
+	  countdown <= 0;
+       end
+     else 
+       begin
+	  send_xon_int <= 0;
+	  send_xoff_int <= 0;
+	  if(countdown == 0)
+	    if(fifo_space < LWMARK)
+	      begin
+		 send_xoff_int <= 1;
+		 countdown <= 240;
+	      end
+	    else
+	      ;
+	  else
+	    if(fifo_space > HWMARK)
+	      begin
+		 send_xon_int <= 1;
+		 countdown <= 0;
+	      end
+	    else
+	      countdown <= countdown - 1;
+       end // else: !if(rst)
+
+   // If we are between the high and low water marks, we let the countdown expire
+
+   always @(posedge clk)
+     if(rst)
+       send_xon <= 0;
+     else if(send_xon_int)
+       send_xon <= 1;
+     else if(sent)
+       send_xon <= 0;
+
+   always @(posedge clk)
+     if(rst)
+       send_xoff <= 0;
+     else if(send_xoff_int)
+       send_xoff <= 1;
+     else if(sent)
+       send_xoff <= 0;
+   
+endmodule // serdes_fc_rx
diff --git a/fpga/usrp2/serdes/serdes_fc_tx.v b/fpga/usrp2/serdes/serdes_fc_tx.v
new file mode 100644
index 000000000..0a62ae2e5
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes_fc_tx.v
@@ -0,0 +1,41 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+
+module serdes_fc_tx
+  (input clk, input rst,
+   input xon_rcvd, input xoff_rcvd, output reg inhibit_tx);
+
+   // XOFF means stop sending, XON means start sending
+   // clock domain stuff happens elsewhere, everything here is on main clk
+
+   reg [15:0] state;
+   always @(posedge clk)
+     if(rst)
+       state <= 0;
+     else if(xoff_rcvd)
+       state <= 255;
+     else if(xon_rcvd)
+       state <= 0;
+     else if(state !=0)
+       state <= state - 1;
+
+   always @(posedge clk)
+     inhibit_tx <= (state != 0);
+   
+endmodule // serdes_fc_tx
diff --git a/fpga/usrp2/serdes/serdes_rx.v b/fpga/usrp2/serdes/serdes_rx.v
new file mode 100644
index 000000000..1950d4e2a
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes_rx.v
@@ -0,0 +1,310 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+// SERDES Interface
+
+// LS-Byte is sent first, MS-Byte is second
+// Invalid K Codes
+//  K0.0  000-00000  Error detected
+//  K31.7 111-11111  Loss of input signal
+
+// Valid K Codes
+//  K28.0 000-11100
+//  K28.1 001-11100  Alternate COMMA?
+//  K28.2 010-11100
+//  K28.3 011-11100
+//  K28.4 100-11100
+//  K28.5 101-11100  Standard COMMA?
+//  K28.6 110-11100
+//  K28.7 111-11100  Bad COMMA?
+//  K23.7 111-10111
+//  K27.7 111-11011
+//  K29.7 111-11101
+//  K30.7 111-11110
+
+module serdes_rx
+  #(parameter FIFOSIZE = 9)
+    (input clk,
+     input rst,
+     
+     // RX HW Interface
+     input ser_rx_clk,
+     input [15:0] ser_r,
+     input ser_rklsb,
+     input ser_rkmsb,
+     
+     output [31:0] wr_dat_o,
+     output [3:0] wr_flags_o,
+     input wr_ready_i,
+     output wr_ready_o,
+     
+     output [15:0] fifo_space,
+     output xon_rcvd, output xoff_rcvd,
+
+     output [15:0] fifo_occupied, output fifo_full, output fifo_empty,
+     output reg serdes_link_up,
+     output [31:0] debug
+     );
+
+   localparam K_COMMA = 8'b101_11100;     // 0xBC K28.5
+   localparam K_IDLE = 8'b001_11100;      // 0x3C K28.1
+   localparam K_PKT_START = 8'b110_11100; // 0xDC K28.6
+   localparam K_PKT_END = 8'b100_11100;   // 0x9C K28.4
+   localparam K_XON = 8'b010_11100;       // 0x5C K28.2
+   localparam K_XOFF = 8'b011_11100;      // 0x7C K28.3
+   localparam K_LOS = 8'b111_11111;       // 0xFF K31.7
+   localparam K_ERROR = 8'b000_00000;     // 0x00 K00.0
+   localparam D_56 = 8'b110_00101;        // 0xC5 D05.6
+   
+   localparam IDLE = 3'd0;
+   localparam FIRSTLINE1 = 3'd1;
+   localparam FIRSTLINE2 = 3'd2;
+   localparam PKT1 = 3'd3;
+   localparam PKT2 = 3'd4;
+   localparam CRC_CHECK = 3'd5;
+   localparam ERROR = 3'd6;
+   localparam DONE = 3'd7;
+   
+   wire [17:0] even_data;
+   reg [17:0]  odd_data;
+   wire [17:0] chosen_data;
+   reg 	       odd;
+   
+   reg [31:0]  line_i;
+   reg 	       sop_i, eop_i, error_i;
+   wire        error_o, sop_o, eop_o, write;
+   reg [15:0]  halfline;
+   reg [8:0]   holder;
+   wire [31:0] line_o;
+   
+   reg [2:0]   state;
+
+   reg [15:0]  CRC;
+   wire [15:0] nextCRC;
+   reg 	       write_d;
+
+   wire        rst_rxclk;
+   wire        have_space;
+
+   oneshot_2clk rst_1s(.clk_in(clk),.in(rst),.clk_out(ser_rx_clk),.out(rst_rxclk));
+
+   assign      even_data = {ser_rkmsb,ser_rklsb,ser_r};
+   
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk)
+       holder <= 9'd0;
+     else
+       holder <= {even_data[17],even_data[15:8]};
+   
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk)
+       odd_data <= 18'd0;
+     else
+       odd_data <= {even_data[16],holder[8],even_data[7:0],holder[7:0]};
+   
+   assign      chosen_data = odd ? odd_data : even_data;
+
+   // Transfer xon and xoff info to the main system clock for flow control purposes
+   reg 	       xon_rcvd_rxclk, xoff_rcvd_rxclk;
+   always @(posedge ser_rx_clk)
+     xon_rcvd_rxclk = ({1'b1,K_XON} == {ser_rkmsb,ser_r[15:8]}) | ({1'b1,K_XON} == {ser_rklsb,ser_r[7:0]} );
+   always @(posedge ser_rx_clk)
+     xoff_rcvd_rxclk = ({1'b1,K_XOFF} == {ser_rkmsb,ser_r[15:8]}) | ({1'b1,K_XOFF} == {ser_rklsb,ser_r[7:0]} );
+   
+   oneshot_2clk xon_1s(.clk_in(ser_rx_clk),.in(xon_rcvd_rxclk),.clk_out(clk),.out(xon_rcvd));
+   oneshot_2clk xoff_1s(.clk_in(ser_rx_clk),.in(xoff_rcvd_rxclk),.clk_out(clk),.out(xoff_rcvd));
+
+   // If the other side is sending xon or xoff, or is flow controlled (b/c we told them to be), don't fill the fifos
+   wire        wait_here = ((chosen_data == {2'b10,K_COMMA,D_56})||
+			    (chosen_data == {2'b11,K_XON,K_XON})||
+			    (chosen_data == {2'b11,K_XOFF,K_XOFF}) );
+
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk) sop_i <= 0;
+     else if(state == FIRSTLINE1) sop_i <= 1;
+     else if(write_d) sop_i <= 0;
+   
+   reg 	       write_pre;
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk)
+       begin
+	  state <= IDLE;
+	  odd <= 0;
+	  halfline <= 0;
+	  line_i <= 0;
+	  eop_i <= 0;
+	  error_i <= 0;
+	  write_pre <= 0;
+       end
+     else
+       case(state)
+	 IDLE :
+	   begin
+	      error_i <= 0;
+	      write_pre <= 0;
+	      if(even_data == {2'b11,K_PKT_START,K_PKT_START})
+		begin
+		   state <= FIRSTLINE1;
+		   odd <= 0;
+		end
+	      else if(odd_data == {2'b11,K_PKT_START,K_PKT_START})
+		begin
+		   state <= FIRSTLINE1;
+		   odd <= 1;
+		end
+	   end
+
+	 FIRSTLINE1 :
+	   if(chosen_data[17:16] == 0)
+	     begin
+		halfline <= chosen_data[15:0];
+		state <= FIRSTLINE2;
+	     end
+	   else if(wait_here)
+	     ;  // Flow Controlled, so wait here and do nothing
+	   else
+	     state <= ERROR;
+
+	 FIRSTLINE2 :
+	   if(chosen_data[17:16] == 0)
+	     begin
+		line_i <= {chosen_data[15:0],halfline};
+		if(~have_space)  // No space to write to!  Should have been avoided by flow control
+		  state <= ERROR;
+		else
+		  begin
+		     state <= PKT1;
+		     write_pre <= 1;
+		  end
+	     end // if (chosen_data[17:16] == 0)
+	   else if(wait_here)
+	     ;  // Flow Controlled, so wait here and do nothing
+	   else
+	     state <= ERROR;
+	 
+	 PKT1 :
+	   begin
+	      write_pre <= 0;
+	      if(chosen_data[17:16] == 0)
+		begin
+		   halfline <= chosen_data[15:0];
+		   state <= PKT2;
+		end
+	      else if(wait_here)
+		;  // Flow Controlled
+	      else if(chosen_data == {2'b11,K_PKT_END,K_PKT_END})
+	  	state <= CRC_CHECK;
+	      else
+		state <= ERROR;
+	   end // case: PKT1
+	 
+	 PKT2 :
+	   if(chosen_data[17:16] == 0)
+	     begin
+		line_i <= {1'b0,1'b0,1'b0,chosen_data[15:0],halfline};
+		if(~have_space)  // No space to write to!
+		  state <= ERROR;
+		else
+		  begin
+		     state <= PKT1;
+		     write_pre <= 1;
+		  end
+	     end // if (chosen_data[17:16] == 0)
+	   else if(wait_here)
+	     ;  // Flow Controlled
+	   else
+	     state <= ERROR;
+	   
+	 CRC_CHECK :
+	   if(chosen_data[17:0] == {2'b00,CRC})
+	     begin
+		if(~have_space)
+		  state <= ERROR;
+		else
+		  begin
+		     eop_i <= 1;
+		     state <= DONE;
+		  end
+	     end
+	   else if(wait_here)
+	     ;
+	   else
+	     state <= ERROR;
+	 
+	 ERROR :
+	   begin
+	      error_i <= 1;
+	      if(have_space)
+		state <= IDLE;
+	   end
+	 DONE :
+	   begin
+	      state <= IDLE;
+	      eop_i <= 0;
+	   end
+	      
+       endcase // case(state)
+   
+   
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk)
+       CRC <= 16'hFFFF;
+     else if(state == IDLE)
+       CRC <= 16'hFFFF;
+     else if(chosen_data[17:16] == 2'b00)
+       CRC <= nextCRC;
+
+   CRC16_D16 crc_blk(chosen_data[15:0],CRC,nextCRC);
+
+   always @(posedge ser_rx_clk)
+     if(rst_rxclk) write_d <= 0;
+     else write_d <= write_pre;
+
+   // Internal FIFO, size 9 is 2K, size 10 is 4K Bytes
+   assign write = eop_i | (error_i & have_space) | (write_d & (state != CRC_CHECK));
+   wire dummy; // avoid warning on unconnected pin
+   
+   fifo_2clock_cascade #(.WIDTH(36),.SIZE(FIFOSIZE)) serdes_rx_fifo
+     (.arst(rst),
+      .wclk(ser_rx_clk),.datain({1'b0,error_i,sop_i,eop_i,line_i}), 
+      .src_rdy_i(write), .dst_rdy_o(have_space), .space(fifo_space), 
+      .rclk(clk),.dataout({dummy,error_o,sop_o,eop_o,line_o}), 
+      .src_rdy_o(wr_ready_o), .dst_rdy_i(wr_ready_i), .occupied(fifo_occupied) );
+
+   assign 	       fifo_full = ~have_space;   // Note -- in the wrong clock domain
+   assign 	       fifo_empty = ~wr_ready_o;
+   
+   // Internal FIFO to Buffer interface
+   assign wr_dat_o 		      = line_o;
+   assign wr_flags_o = { 2'b00, eop_o | error_o, sop_o | error_o };
+   
+   wire slu = ~(({2'b11,K_ERROR,K_ERROR}=={ser_rkmsb,ser_rklsb,ser_r}) ||
+		       ({2'b11,K_LOS,K_LOS}=={ser_rkmsb,ser_rklsb,ser_r}));
+   
+   reg [3:0]   slu_reg;
+   
+   always @(posedge clk)
+     if(rst) slu_reg <= 0;
+     else slu_reg <= {slu_reg[2:0],slu};
+
+   always @(posedge clk)
+     serdes_link_up <= &slu_reg[3:1];
+   
+   assign      debug = { have_space, wr_ready_o, odd, sop_i, eop_i, error_i, state[2:0] };
+   
+endmodule // serdes_rx
diff --git a/fpga/usrp2/serdes/serdes_tb.v b/fpga/usrp2/serdes/serdes_tb.v
new file mode 100644
index 000000000..685a8580d
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes_tb.v
@@ -0,0 +1,345 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+// FIXME need to add flow control
+
+module serdes_tb();
+   
+   reg clk, rst;
+   wire ser_rx_clk, ser_tx_clk;
+   wire ser_rklsb, ser_rkmsb, ser_tklsb, ser_tkmsb;
+   wire [15:0] ser_r, ser_t;
+   
+   initial clk = 0;
+   initial rst = 1;
+   initial #1000 rst = 0;
+   always #100 clk = ~clk;
+   
+   // Wishbone
+   reg [31:0]  wb_dat_i;
+   wire [31:0] wb_dat_o_rx, wb_dat_o_tx;
+   reg 	       wb_we, wb_en_rx, wb_en_tx;
+   reg [8:0]   wb_adr;
+
+   // Buffer Control
+   reg 	       go, clear, read, write;
+   reg [3:0]   buf_num;
+   wire [31:0] ctrl_word = {buf_num,3'b0,clear,write,read,step,lastline,firstline};
+   reg [8:0]   firstline = 0, lastline = 0;
+   reg [3:0]   step = 1;
+   reg 	       first_tx = 1, first_rx = 1;  // for verif
+   
+   // TX Side
+   reg 	       wb_we_tx;
+   wire        en_tx, we_tx;
+   wire [8:0]  addr_tx;
+   wire [31:0] f2r_tx, r2f_tx;
+   wire [31:0] data_tx;
+   wire        read_tx, done_tx, error_tx, sop_tx, eop_tx;
+   
+   wire        fdone_tx, ferror_tx;
+   
+   reg 	       even;
+   reg 	       channel_error = 0;
+   
+   serdes_tx serdes_tx
+     (.clk(clk),.rst(rst),
+      .ser_tx_clk(ser_tx_clk),.ser_t(ser_t),.ser_tklsb(ser_tklsb),.ser_tkmsb(ser_tkmsb),
+      .rd_dat_i(data_tx),.rd_read_o(read_tx),.rd_done_o(done_tx),
+      .rd_error_o(error_tx),.rd_sop_i(sop_tx),.rd_eop_i(eop_tx) );
+   
+   ram_2port #(.DWIDTH(32),.AWIDTH(9))
+     ram_tx(.clka(clk),.ena(wb_en_tx),.wea(wb_we_tx),.addra(wb_adr),.dia(wb_dat_i),.doa(wb_dat_o_tx),
+            .clkb(clk),.enb(en_tx),.web(we_tx),.addrb(addr_tx),.dib(f2r_tx),.dob(r2f_tx));
+   
+   buffer_int #(.BUFF_NUM(1)) buffer_int_tx
+     (.clk(clk),.rst(rst),
+      .ctrl_word(ctrl_word),.go(go),
+      .done(fdone_tx),.error(ferror_tx),
+      
+      .en_o(en_tx),.we_o(we_tx),.addr_o(addr_tx),.dat_to_buf(f2r_tx),.dat_from_buf(r2f_tx),
+      
+      .wr_dat_i(0),.wr_write_i(0),.wr_done_i(0),
+      .wr_error_i(0),.wr_ready_o(),.wr_full_o(),
+      
+      .rd_dat_o(data_tx),.rd_read_i(read_tx),.rd_done_i(done_tx),
+      .rd_error_i(error_tx),.rd_sop_o(sop_tx),.rd_eop_o(eop_tx) );
+
+
+   // RX Side
+   reg 	       wb_we_rx;
+   wire        en_rx, we_rx;
+   wire [8:0]  addr_rx;
+   wire [31:0] f2r_rx, r2f_rx;
+   wire [31:0] data_rx;
+   wire        write_rx, done_rx, error_rx, ready_rx, empty_rx;
+   
+   wire        fdone_rx, ferror_rx;
+   
+   serdes_rx serdes_rx
+     (.clk(clk),.rst(rst),
+      .ser_rx_clk(ser_rx_clk),.ser_r(ser_r),.ser_rklsb(ser_rklsb),.ser_rkmsb(ser_rkmsb),
+      .wr_dat_o(data_rx),.wr_write_o(write_rx),.wr_done_o(done_rx),
+      .wr_error_o(error_rx),.wr_ready_i(ready_rx),.wr_full_i(full_rx) );
+
+   ram_2port #(.DWIDTH(32),.AWIDTH(9))
+     ram_rx(.clka(clk),.ena(wb_en_rx),.wea(wb_we_rx),.addra(wb_adr),.dia(wb_dat_i),.doa(wb_dat_o_rx),
+            .clkb(clk),.enb(en_rx),.web(we_rx),.addrb(addr_rx),.dib(f2r_rx),.dob(r2f_rx) );
+   
+   buffer_int #(.BUFF_NUM(0)) buffer_int_rx
+     (.clk(clk),.rst(rst),
+      .ctrl_word(ctrl_word),.go(go),
+      .done(fdone_rx),.error(ferror_rx),
+      
+      .en_o(en_rx),.we_o(we_rx),.addr_o(addr_rx),.dat_to_buf(f2r_rx),.dat_from_buf(r2f_rx),
+      
+      .wr_dat_i(data_rx),.wr_write_i(write_rx),.wr_done_i(done_rx),
+      .wr_error_i(error_rx),.wr_ready_o(ready_rx),.wr_full_o(full_rx),
+      
+      .rd_dat_o(),.rd_read_i(0),.rd_done_i(0),
+      .rd_error_i(0),.rd_sop_o(),.rd_eop_o() );
+
+   // Simulate the connection
+   serdes_model serdes_model
+     (.ser_tx_clk(ser_tx_clk), .ser_tkmsb(ser_tkmsb), .ser_tklsb(ser_tklsb), .ser_t(ser_t),
+      .ser_rx_clk(ser_rx_clk), .ser_rkmsb(ser_rkmsb), .ser_rklsb(ser_rklsb), .ser_r(ser_r),
+      .even(even), .error(channel_error) );
+   
+   initial begin
+      wb_en_rx <= 0;
+      wb_en_tx <=0;
+      wb_we_tx <= 0;
+      wb_we_rx <= 0;
+      wb_adr <= 0;
+      wb_dat_i <= 0;
+      go <= 0;
+      even <= 0;
+      @(negedge rst);
+      @(posedge clk);
+      FillTXRAM;
+      ClearRXRAM;
+      ResetBuffer(0);
+      ResetBuffer(1);
+
+      // receive a full buffer
+      ReceiveSERDES(0,10);
+      SendSERDES(0,10);
+
+      // Receive a partial buffer
+      SendSERDES(11,20);
+      ReceiveSERDES(11,50);
+
+      // Receive too many for buffer
+      SendSERDES(21,100);
+      ReceiveSERDES(21,30);
+
+      // Send 3 packets, then wait to receive them, so they stack up in the rx fifo
+      SendSERDES(31,40);
+      SendSERDES(41,50);
+      SendSERDES(51,60);
+      repeat (10)
+	@(posedge clk);
+      ReceiveSERDES(31,40);
+      ReceiveSERDES(41,50);
+      repeat (1000)
+	@(posedge clk);
+      ReceiveSERDES(51,60);
+
+      // Overfill the FIFO, should get an error on 3rd packet
+      SendSERDES(1,400);
+      SendSERDES(1,400);
+      
+      
+      WaitForTX;
+      //WaitForRX;
+      
+
+      repeat(1000)
+	@(posedge clk);
+      ReceiveSERDES(101,500);
+      ReceiveSERDES(101,500);
+      ReadRAM(80);
+      $finish;
+   end // initial begin
+
+   always @(posedge clk)
+     if(write_rx)
+       $display("SERDES RX, FIFO WRITE %x, FIFO RDY %d, FIFO FULL %d",data_rx, ready_rx, full_rx);
+   
+   always @(posedge clk)
+     if(read_tx)
+       $display("SERDES TX, FIFO READ %x, SOP %d, EOP %d",data_tx, sop_tx, eop_tx);
+   
+   initial begin
+      $dumpfile("serdes_tb.vcd");
+      $dumpvars(0,serdes_tb);
+   end
+
+   initial #10000000 $finish;
+
+   initial #259300 channel_error <= 1;
+   initial #259500 channel_error <= 0;
+   
+   task FillTXRAM;
+      begin
+	 wb_adr <= 0;
+	 wb_dat_i <= 32'h10802000;
+	 wb_we_tx <= 1;
+	 wb_en_tx <= 1;
+	 @(posedge clk);
+	 repeat(511) begin
+	    wb_dat_i <= wb_dat_i + 32'h00010001;
+	    wb_adr <= wb_adr + 1;
+	    @(posedge clk);
+	 end // repeat (511)
+	 wb_we_tx <= 0;
+	 wb_en_tx <= 0;
+	 @(posedge clk);
+	 $display("Done entering Data into TX RAM\n");
+      end
+   endtask // FillTXRAM
+   
+   task ClearRXRAM;
+      begin
+	 wb_adr <= 0;
+	 wb_dat_i <= 0;
+	 wb_we_rx <= 1;
+	 wb_en_rx <= 1;
+	 wb_dat_i <= 0;
+	 @(posedge clk);
+	 repeat(511) begin
+	    wb_adr <= wb_adr + 1;
+	    @(posedge clk);
+	 end // repeat (511)
+	 wb_we_rx <= 0;
+	 wb_en_rx <= 0;
+	 @(posedge clk);
+	 $display("Done clearing RX RAM\n");
+      end
+   endtask // FillRAM
+   
+   task ReadRAM;
+      input [8:0] lastline;
+      begin
+	 wb_en_rx <= 1;
+	 wb_adr <= 0;
+	 @(posedge clk);
+	 @(posedge clk);
+	 repeat(lastline) begin
+	    $display("ADDR: %h  DATA %h", wb_adr, wb_dat_o_rx);
+	    wb_adr <= wb_adr + 1;
+	    @(posedge clk);
+	    @(posedge clk);
+	 end // repeat (511)
+	 $display("ADDR: %h  DATA %h", wb_adr, wb_dat_o_rx);
+	 wb_en_rx <= 0;
+	 @(posedge clk);
+	 $display("Done reading out RX RAM\n");
+      end
+   endtask // FillRAM
+   
+   task ResetBuffer;
+      input [3:0] buffer_num;
+      begin
+	 buf_num <= buffer_num;
+	 clear <= 1; read <= 0; write <= 0;
+	 go <= 1;
+	 @(posedge clk);
+	 go <= 0;
+	 @(posedge clk);
+	 $display("Buffer Reset");
+      end
+   endtask // ClearBuffer
+   
+   task SetBufferWrite;
+      input [3:0] buffer_num;
+      input [8:0] start;
+      input [8:0] stop;
+      begin
+	 buf_num <= buffer_num;
+	 clear <= 0; read <= 0; write <= 1;
+	 firstline <= start;
+	 lastline <= stop;
+	 go <= 1;
+	 @(posedge clk);
+	 go <= 0;
+	 @(posedge clk);
+	 $display("Buffer Set for Write");
+      end
+   endtask // SetBufferWrite
+   
+   task SetBufferRead;
+      input [3:0] buffer_num;
+      input [8:0] start;
+      input [8:0] stop;
+      begin
+	 buf_num <= buffer_num;
+	 clear <= 0; read <= 1; write <= 0;
+	 firstline <= start;
+	 lastline <= stop;
+	 go <= 1;
+	 @(posedge clk);
+	 go <= 0;
+	 @(posedge clk);
+	 $display("Buffer Set for Read");
+      end
+   endtask // SetBufferRead
+
+   task WaitForTX;
+      begin
+	 while (!(fdone_tx | ferror_tx))
+	   @(posedge clk);
+      end
+   endtask // WaitForTX
+   
+   task WaitForRX;
+      begin
+	 while (!(fdone_rx | ferror_rx))
+	   @(posedge clk);
+      end
+   endtask // WaitForRX
+   
+   task SendSERDES;
+      input [8:0] start;
+      input [8:0] stop;
+      begin
+	 if(~first_tx)
+	   WaitForTX;
+	 else
+	   first_tx <= 0;
+	 ResetBuffer(1);
+	 SetBufferRead(1,start,stop);
+	 $display("Here");
+      end
+   endtask // SendSERDES
+   
+   task ReceiveSERDES;
+      input [8:0] start;
+      input [8:0] stop;
+      begin
+	 if(~first_rx)
+	   WaitForRX;
+	 else
+	   first_rx <= 0;
+	 ResetBuffer(0);
+	 SetBufferWrite(0,start,stop);
+	 $display("Here2");
+      end
+   endtask // ReceiveSERDES
+   
+endmodule // serdes_tb
diff --git a/fpga/usrp2/serdes/serdes_tx.v b/fpga/usrp2/serdes/serdes_tx.v
new file mode 100644
index 000000000..0cd077e5c
--- /dev/null
+++ b/fpga/usrp2/serdes/serdes_tx.v
@@ -0,0 +1,203 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: 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
+// MERCHANTABILITY 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.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+// SERDES Interface
+
+// LS-Byte is sent first, MS-Byte is second
+// Invalid K Codes
+//  K0.0  000-00000  Error detected
+//  K31.7 111-11111  Loss of input signal
+
+// Valid K Codes
+//  K28.0 000-11100
+//  K28.1 001-11100  Alternate COMMA?
+//  K28.2 010-11100
+//  K28.3 011-11100
+//  K28.4 100-11100
+//  K28.5 101-11100  Standard COMMA?
+//  K28.6 110-11100
+//  K28.7 111-11100  Bad COMMA?
+//  K23.7 111-10111
+//  K27.7 111-11011
+//  K29.7 111-11101
+//  K30.7 111-11110
+
+module serdes_tx
+  #(parameter FIFOSIZE = 9)
+    (input clk,
+     input rst,
+     
+     // TX HW Interface
+     output ser_tx_clk,
+     output reg [15:0] ser_t,
+     output reg ser_tklsb,
+     output reg ser_tkmsb,
+     
+     // TX Stream Interface
+     input [31:0] rd_dat_i,
+     input [3:0] rd_flags_i,
+     output rd_ready_o,
+     input rd_ready_i,
+
+     // Flow control interface
+     input inhibit_tx,
+     input send_xon,
+     input send_xoff,
+     output sent,
+
+     // FIFO Levels
+     output [15:0] fifo_occupied,
+     output fifo_full,
+     output fifo_empty,
+
+     // DEBUG
+     output [31:0] debug
+     );
+
+   localparam K_COMMA = 8'b101_11100;     // 0xBC K28.5
+   localparam K_IDLE = 8'b001_11100;      // 0x3C K28.1
+   localparam K_PKT_START = 8'b110_11100; // 0xDC K28.6
+   localparam K_PKT_END = 8'b100_11100;   // 0x9C K28.4
+   localparam K_XON = 8'b010_11100;       // 0x5C K28.2
+   localparam K_XOFF = 8'b011_11100;      // 0x7C K28.3
+   localparam K_LOS = 8'b111_11111;       // 0xFF K31.7
+   localparam K_ERROR = 8'b000_00000;     // 0x00 K00.0
+   localparam D_56 = 8'b110_00101;        // 0xC5 D05.6
+   assign     ser_tx_clk = clk;
+   
+   localparam IDLE = 3'd0;
+   localparam RUN1 = 3'd1;
+   localparam RUN2 = 3'd2;
+   localparam DONE = 3'd3;
+   localparam SENDCRC = 3'd4;
+   localparam WAIT = 3'd5;
+   
+   reg [2:0]  state;
+   
+   reg [15:0] CRC;
+   wire [15:0] nextCRC;
+   reg [3:0]   wait_count;
+   
+   // Internal FIFO, size 9 is 2K, size 10 is 4K bytes
+   wire        sop_o, eop_o;
+   wire [31:0] data_o;
+
+   wire        rd_sop_i  = rd_flags_i[0];
+   wire        rd_eop_i  = rd_flags_i[1];
+   wire [1:0]  rd_occ_i = rd_flags_i[3:2];  // Unused
+
+   wire        have_data, empty, read;
+   fifo_cascade #(.WIDTH(34),.SIZE(FIFOSIZE)) serdes_tx_fifo
+     (.clk(clk),.reset(rst),.clear(0),
+      .datain({rd_sop_i,rd_eop_i,rd_dat_i}), .src_rdy_i(rd_ready_i), .dst_rdy_o(rd_ready_o),
+      .dataout({sop_o,eop_o,data_o}), .dst_rdy_i(read), .src_rdy_o(have_data),
+      .space(), .occupied(fifo_occupied) );
+   
+   assign fifo_full   = ~rd_ready_o;
+   assign empty       = ~have_data;
+   assign fifo_empty  = empty;
+   
+   // FIXME Implement flow control   
+   reg [15:0]  second_word;
+   reg [33:0]  pipeline;
+   
+   assign      read = (~send_xon & ~send_xoff & (state==RUN2)) | ((state==IDLE) & ~empty & ~sop_o);
+   assign      sent = send_xon | send_xoff;
+   // 2nd half of above probably not necessary.  Just in case we get junk between packets
+   
+   always @(posedge clk)
+     if(rst)
+       begin
+	  state <= IDLE;
+	  wait_count <= 0;
+	  {ser_tkmsb,ser_tklsb,ser_t} <= 18'd0;
+			//{2'b10,K_COMMA,K_COMMA};  
+	  // make tkmsb and tklsb different so they can go in IOFFs
+       end
+     else
+       if(send_xon)
+	 {ser_tkmsb,ser_tklsb,ser_t} <= {2'b11,K_XON,K_XON};
+       else if(send_xoff)
+	 {ser_tkmsb,ser_tklsb,ser_t} <= {2'b11,K_XOFF,K_XOFF};
+       else
+	 case(state)
+	   IDLE :
+	     begin
+		if(sop_o & ~empty & ~inhibit_tx)
+		  begin
+		     {ser_tkmsb,ser_tklsb,ser_t} <= {2'b11,K_PKT_START,K_PKT_START};
+		     state <= RUN1;
+		  end
+		else
+		  {ser_tkmsb,ser_tklsb,ser_t} <= {2'b10,K_COMMA,D_56};
+	     end
+	   RUN1 :
+	     begin
+		if(empty | inhibit_tx)
+		  {ser_tkmsb,ser_tklsb,ser_t} <= {2'b10,K_COMMA,D_56};
+		else
+		  begin
+		     {ser_tkmsb,ser_tklsb,ser_t} <= {2'b00,data_o[15:0]};
+		     state <= RUN2;
+		  end
+	     end
+	   RUN2 :
+	     begin
+		{ser_tkmsb,ser_tklsb,ser_t} <= {2'b00,data_o[31:16]};
+		if(eop_o)
+		  state <= DONE;
+		else
+		  state <= RUN1;
+	     end
+	   DONE :
+	     begin
+		{ser_tkmsb,ser_tklsb,ser_t} <= {2'b11,K_PKT_END,K_PKT_END};
+		state <= SENDCRC;
+	     end
+	   SENDCRC :
+	     begin
+		{ser_tkmsb,ser_tklsb,ser_t} <= {2'b00,CRC};
+		state <= WAIT;
+		wait_count <= 4'd15;
+	     end
+	   WAIT :
+	     begin
+		{ser_tkmsb,ser_tklsb,ser_t} <= {2'b10,K_COMMA,D_56};
+		if(wait_count == 0)
+		  state <= IDLE;
+		else
+		  wait_count <= wait_count - 1;
+	     end
+	   default
+	     state <= IDLE;
+	 endcase // case(state)
+   
+   always @(posedge clk)
+     if(rst)
+       CRC <= 16'hFFFF;
+     else if(state == IDLE)
+       CRC <= 16'hFFFF;
+     else if( (~empty & ~inhibit_tx & (state==RUN1)) || (state==RUN2) )
+       CRC <= nextCRC;
+   
+   CRC16_D16 crc_blk( (state==RUN1) ? data_o[15:0] : data_o[31:16], CRC, nextCRC);
+
+   assign debug = { 28'd0, state[2:0] };
+   
+endmodule // serdes_tx
+