fpga: x400: Add support for X410 motherboard FPGA

Co-authored-by: Andrew Moch <Andrew.Moch@ni.com>
Co-authored-by: Daniel Jepson <daniel.jepson@ni.com>
Co-authored-by: Javier Valenzuela <javier.valenzuela@ni.com>
Co-authored-by: Joerg Hofrichter <joerg.hofrichter@ni.com>
Co-authored-by: Kumaran Subramoniam <kumaran.subramoniam@ni.com>
Co-authored-by: Max Köhler <max.koehler@ni.com>
Co-authored-by: Michael Auchter <michael.auchter@ni.com>
Co-authored-by: Paul Butler <paul.butler@ni.com>
Co-authored-by: Wade Fife <wade.fife@ettus.com>
Co-authored-by: Hector Rubio <hrubio@ni.com>

1 files changed, 99 insertions, 0 deletions

diff --git a/fpga/usrp3/top/x400/rf/400m/dac_gearbox_6x8.vhd b/fpga/usrp3/top/x400/rf/400m/dac_gearbox_6x8.vhd
new file mode 100644
index 000000000..c673cd732
--- /dev/null
+++ b/fpga/usrp3/top/x400/rf/400m/dac_gearbox_6x8.vhd
@@ -0,0 +1,99 @@
+--
+-- Copyright 2021 Ettus Research, a National Instruments Brand
+--
+-- SPDX-License-Identifier: LGPL-3.0-or-later
+--
+-- Module: dac_gearbox_6x8
+--
+-- Description:
+--
+--   Gearbox to expand the data width from 6 SPC to 8 SPC.
+--   Input Clocks, all aligned to one another and coming from same MMCM
+--     PLL reference clock = 61.44 or 62.5 MHz.
+--     RfClk:       184.32 or 187.5 MHz (3x PLL reference clock)
+--     Clk1x:       122.88 or 125 MHz (2x PLL reference clock)
+--     Clk2x:       245.76 or 250 MHz (4x PLL reference clock)
+--
+
+library IEEE;
+  use IEEE.std_logic_1164.all;
+  use IEEE.numeric_std.all;
+
+entity dac_gearbox_6x8 is
+  port(
+    Clk1x           : in  std_logic;
+    Clk2x           : in  std_logic;
+    RfClk           : in  std_logic;
+    ac1Reset_n      : in  std_logic;
+    ac2Reset_n      : in  std_logic;
+    arReset_n       : in  std_logic;
+    -- 16 bit data packing: [Q5,I5,Q4,I4,Q3,I3,Q2,I2,Q1,I1,Q0,I0] (I in LSBs)
+    c2DataIn        : in  std_logic_vector(191 downto 0);
+    c2DataValidIn   : in  std_logic;
+    -- 16 bit data packing: [Q7,I7,Q6,I6,..,Q2,I2,Q1,I1,Q0,I0] (I in LSBs)
+    rDataOut        : out std_logic_vector(255 downto 0) := (others => '0');
+    rReadyForOutput : in  std_logic;
+    rDataValidOut   : out std_logic := '0'
+  );
+end dac_gearbox_6x8;
+
+architecture struct of dac_gearbox_6x8 is
+
+  signal c1DataOut : std_logic_vector(383 downto 0);
+  signal c1DataValidOut : std_logic;
+
+begin
+
+  -- Clk1x, Clk2x, and RfClk are source from the same PLL and have a known
+  -- phase relationship between power cycles. Since, they have known phase
+  -- relationship, clock crossing as be done without a dual clock FIFO or any
+  -- other handshaking mechanism. We cannot move data from Clk2x to RfClk
+  -- because of the clock relation between these two clocks will make it almost
+  -- impossible to close timing. So, we move data from Clk2x to Clk1x and then
+  -- to RfClk domain. Since, we need deterministic delay in the data path, we
+  -- cannot use a FIFO to do data crossing.
+  --
+  -- Clk1x = Sample clock/24
+  -- Clk2x = Sample clock/12
+  -- RfClk = Sample clock/16
+  --
+  -- Clk1x __/-----\_____/-----\_____/-----\_____/-----\_____/-----\___
+  --                                             |   |
+  -- Clk2x __/--\__/--\__/--\__/--\__/--\        |   |
+  --               | |                           |   |
+  --               | | <- Setup relationship     |   | <- Setup relationship
+  --               | |                           |   |
+  -- RfClk __/---\___/---\___/---\___/---\___/---\___/---\___/---\___/-
+  --
+  -- As you can see the setup relationship for passing data synchronously from
+  -- Clk2x to RfClk is very small (Sample clock period * 4). It is not possible
+  -- to close timing with this requirement. For passing data from Clk1x to
+  -- RfClk the setup relationship is (Sample clock period * 8) which is
+  -- relatively easy to close timing.
+
+  dac_gearbox_6x12_i: entity work.dac_gearbox_6x12 (RTL)
+    port map (
+      Clk1x          => Clk1x,
+      Clk2x          => Clk2x,
+      ac1Reset_n     => ac1Reset_n,
+      ac2Reset_n     => ac2Reset_n,
+      c2DataIn       => c2DataIn,
+      c2DataValidIn  => c2DataValidIn,
+      c1DataOut      => c1DataOut,
+      c1DataValidOut => c1DataValidOut
+    );
+
+  dac_gearbox_12x8_i: entity work.dac_gearbox_12x8 (RTL)
+    port map (
+      Clk1x           => Clk1x,
+      RfClk           => RfClk,
+      ac1Reset_n      => ac1Reset_n,
+      arReset_n       => arReset_n,
+      c1DataIn        => c1DataOut,
+      c1DataValidIn   => c1DataValidOut,
+      rDataOut        => rDataOut,
+      rReadyForOutput => rReadyForOutput,
+      rDataValidOut   => rDataValidOut
+    );
+
+end struct;