1 files changed, 106 insertions, 0 deletions
diff --git a/fpga/usrp3/top/x300/gen_ddrlvds.v b/fpga/usrp3/top/x300/gen_ddrlvds.v
new file mode 100644
index 000000000..5773b296c
--- /dev/null
+++ b/fpga/usrp3/top/x300/gen_ddrlvds.v
@@ -0,0 +1,106 @@
+
+
+module gen_ddrlvds
+  (
+   // 1X Radio Clock
+   input tx_clk_1x,
+   // 2X Radio clock
+   input tx_clk_2x,
+   // Clk to drive DCI ODDR. This is a phase shifted version of
+   // tx_clk_2x. The phase shift is to center the DCI edge in the
+   // valid window of the data in the DAC.
+   input tx_dci_clk,
+   // Reset signal synchronous to radio clock
+   input reset,
+   // Source synchronous differential clocks to DAC
+   output tx_clk_2x_p, 
+   output tx_clk_2x_n,
+   // Differential frame sync to DAC
+   output tx_frame_p, 
+   output tx_frame_n,
+   // Differential byte wide data to DAC.
+   // Alternates I[15:8],I[7:0],Q[15:8],Q[7:0]
+   output [7:0] tx_d_p, 
+   output [7:0] tx_d_n,
+   // Input data
+   input [15:0] i, 
+   input [15:0] q,
+   // Rising edge sampled on sync_dacs triggers frame sync sequence
+   input sync_dacs
+   );
+
+   reg [15:0] 	i_reg, q_reg;
+   reg [15:0] 	i_2x, q_2x;
+   reg 		rising_edge;
+   wire [15:0] 	i_and_q_2x;
+   reg 		sync_2x;
+   
+   genvar 	z;
+   wire [7:0] 	tx_int;
+   wire 	tx_clk_2x_int;
+   wire 	tx_frame_int;
+
+   // Keep constraint to ensure these signals are not resource shared which can cause timing failures
+   (* keep = "true" *) reg phase, phase_2x, sync_dacs_reg;
+
+   wire phase_eq_phase2x = (phase == phase_2x);
+
+   always @(posedge tx_clk_1x)
+     if (reset)
+       phase <= 1'b0;
+     else
+       phase <= ~phase;
+
+
+   //
+   // Pipeline input data so that 1x to 2x clock domain jump includes no logic external to this module.
+   //
+   always @(posedge tx_clk_1x) 
+     begin
+	i_reg <= i;
+	q_reg <= q;
+	sync_dacs_reg <= sync_dacs;
+     end  
+
+   always @(posedge tx_clk_2x)
+     begin
+	// Move 1x data to 2x domain, mostly just to add pipeline regs
+	// for timing closure.
+	i_2x <= i_reg;
+	q_2x <= q_reg;
+	// Sample phase to determine when 1x clock edges occur.
+	// To sync multiple AD9146 DAC's an extended assertion of FRAME is required,
+	// when sync flag set, squash one rising_edge assertion which causes a 3 word assertion of FRAME,
+	// also reset sync flag. "sync_dacs" comes from 1x clk and pulse lasts 2 2x clock cycles...this is accounted for.
+	sync_2x <=  (phase_eq_phase2x && sync_2x) ? 1'b0 /*RESET */ : (sync_dacs_reg) ? 1'b1 /* SET */ : sync_2x /* HOLD */;
+	rising_edge <= (phase_eq_phase2x && ~sync_2x);
+	phase_2x <= phase;
+     end
+
+   // Interleave I and Q as SDR signals
+   assign i_and_q_2x = rising_edge ? q_2x : i_2x;
+   
+   generate	
+      for(z = 0; z < 8; z = z + 1)
+	begin : gen_pins
+	   OBUFDS obufds (.I(tx_int[z]), .O(tx_d_p[z]), .OB(tx_d_n[z]));
+	   ODDR #(.DDR_CLK_EDGE("SAME_EDGE")) oddr
+	     (.Q(tx_int[z]), .C(tx_clk_2x),
+	      .CE(1'b1), .D1(i_and_q_2x[z+8]), .D2(i_and_q_2x[z]), .S(1'b0), .R(1'b0));
+	end
+   endgenerate
+
+   // Generate framing signal to identify I and Q
+   OBUFDS obufds_frame (.I(tx_frame_int), .O(tx_frame_p), .OB(tx_frame_n));
+   ODDR #(.DDR_CLK_EDGE("SAME_EDGE")) oddr_frame
+     (.Q(tx_frame_int), .C(tx_clk_2x),
+      .CE(1'b1), .D1(~rising_edge), .D2(~rising_edge), .S(1'b0), .R(1'b0));
+
+   // Source synchronous clk
+   OBUFDS obufds_clk (.I(tx_clk_2x_int), .O(tx_clk_2x_p), .OB(tx_clk_2x_n));
+   ODDR #(.DDR_CLK_EDGE("SAME_EDGE")) oddr_clk
+     (.Q(tx_clk_2x_int), .C(tx_dci_clk),
+      .CE(1'b1), .D1(1'b1), .D2(1'b0), .S(1'b0), .R(1'b0));
+
+endmodule // gen_ddrlvds
+