Merge branch 'master' into mwest/b200_docs

1 files changed, 128 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/axi/axi_embed_tlast.v b/fpga/usrp3/lib/axi/axi_embed_tlast.v
new file mode 100644
index 000000000..065f59fd4
--- /dev/null
+++ b/fpga/usrp3/lib/axi/axi_embed_tlast.v
@@ -0,0 +1,128 @@
+//
+// AXI stream neds N+1 bits to transmit packets of N bits so that the LAST bit can be represented.
+// LAST occurs relatively infrequently and can be synthesized by using an in-band ESC code to generate
+// a multi-word sequence to encode it (and the escape character when it appears as data input).
+//
+// 0x1234567887654321 with last becomes
+// 0xDEADBEEFFEEDCAFE 0x0000000000000001 0x1234567887654321
+//
+// 0xDEADBEEFFEEDCAFE with last becomes
+// 0xDEADBEEFFEEDCAFE 0x0000000000000001 0xDEADBEEFFEEDCAFE
+//
+// 0xDEADBEEFFEEDCAFE without last becomes
+// 0xDEADBEEFFEEDCAFE 0x0000000000000000 0xDEADBEEFFEEDCAFE
+//
+
+module axi_embed_tlast
+   #(parameter WIDTH=64)
+  (
+   input clk,
+   input reset,
+   input clear,
+   //
+   input [WIDTH-1:0] i_tdata,
+   input i_tlast,
+   input i_tvalid,
+   output i_tready,
+   //
+   output reg [WIDTH-1:0] o_tdata,
+   output o_tvalid,
+   input o_tready
+   
+   );
+
+   localparam PASS = 0;
+   localparam ZERO = 1;
+   localparam ONE = 2;
+   localparam ESCAPE = 3;
+
+   localparam IDLE = 0;
+   localparam LAST = 1;
+   localparam ESC = 2;
+   localparam FINISH = 3;
+   
+   reg [1:0]  state, next_state;
+
+   reg [1:0]  select;
+
+   reg [31:0] checksum;
+   
+   always @(posedge clk) 
+     if (reset | clear) begin
+	checksum <= 0;
+     end else if (i_tready && i_tvalid && i_tlast) begin
+	checksum <= 0;
+     end else if (i_tready && i_tvalid) begin
+	checksum <= checksum + i_tdata[31:0] + i_tdata[63:32];
+     end 
+   
+   always @(posedge clk) 
+     if (reset | clear) begin
+	state <= IDLE;
+     end else begin if (o_tready)
+	state <= next_state;
+     end 
+   
+   always @(*) begin
+      case(state)
+	IDLE: begin
+	   if (i_tlast && i_tvalid)
+	     begin
+		next_state = LAST;
+		select = ESCAPE;
+	     end
+	   else if ((i_tdata == 64'hDEADBEEFFEEDCAFE) && i_tvalid)
+	     begin
+		next_state = ESC;
+		select = ESCAPE;
+	     end
+	   else
+	     begin
+		next_state = IDLE;
+		select = PASS;
+	     end
+	end // case: IDLE
+	//
+	//
+	LAST: begin
+	   select = ONE;
+	   next_state = FINISH;
+	end
+	//
+	//
+	ESC: begin
+	   select = ZERO;
+	   next_state = FINISH;
+	end
+	//
+	//
+	FINISH: begin
+	   select = PASS;
+	   if (i_tvalid)
+	     next_state = IDLE;
+	   else
+	     next_state = FINISH;
+	end
+      endcase // case(state)
+   end // always @ (*)
+   	      
+   //
+   // Muxes
+   //
+   always @*
+     begin
+	case(select)
+	  PASS:   o_tdata = i_tdata;	  
+	  ZERO:   o_tdata = 0;
+	  ONE:    o_tdata = {checksum[31:0],32'h1};
+	  ESCAPE: o_tdata = 64'hDEADBEEFFEEDCAFE;
+	endcase // case(select)
+     end
+
+   assign o_tvalid = (select == PASS) ? i_tvalid : 1'b1;
+   assign i_tready = (select == PASS) ? o_tready : 1'b0;
+
+endmodule // axi_embed_tlast
+
+
+