1 files changed, 119 insertions, 0 deletions
diff --git a/fpga/usrp3/top/x400/rf/sim/tb_capture_sysref.vhd b/fpga/usrp3/top/x400/rf/sim/tb_capture_sysref.vhd
new file mode 100644
index 000000000..eb5cbcf08
--- /dev/null
+++ b/fpga/usrp3/top/x400/rf/sim/tb_capture_sysref.vhd
@@ -0,0 +1,119 @@
+--
+-- Copyright 2021 Ettus Research, a National Instruments Brand
+--
+-- SPDX-License-Identifier: LGPL-3.0-or-later
+--
+-- Module: tb_capture_sysref
+--
+-- Description:
+--
+--   Self-checking testbench for tb_capture_sysref.
+--
+
+library IEEE;
+  use IEEE.std_logic_1164.all;
+  use IEEE.numeric_std.all;
+
+entity tb_capture_sysref is
+end tb_capture_sysref;
+
+
+architecture RTL of tb_capture_sysref is
+
+  component capture_sysref
+    port (
+      pll_ref_clk     : in  std_logic;
+      rfdc_clk        : in  std_logic;
+      sysref_in       : in  std_logic;
+      enable_rclk     : in  std_logic;
+      sysref_out_pclk : out std_logic;
+      sysref_out_rclk : out std_logic);
+  end component;
+
+  signal enable_rclk     : std_logic := '0';
+  signal sysref_out_pclk : std_logic := '0';
+  signal sysref_out_rclk : std_logic := '0';
+  signal sysref_in       : std_logic := '0';
+
+  signal SysrefDly, SysrefDlyDly, rSysref : std_logic := '0';
+
+  signal StopSim : boolean;
+  constant kPerPRC : time := 30 ns;
+  constant kPerRF  : time := 10 ns;
+
+  signal PllRefClk : std_logic := '1';
+  signal RfdcClk   : std_logic := '1';
+
+  procedure ClkWait(X : positive := 1) is
+  begin
+    for i in 1 to X loop
+      wait until rising_edge(PllRefClk);
+    end loop;
+  end procedure ClkWait;
+
+begin
+
+  PllRefClk <= not PllRefClk after kPerPRC/2 when not StopSim else '0';
+  RfdcClk   <= not RfdcClk   after kPerRF/2  when not StopSim else '0';
+
+  dut: capture_sysref
+    port map (
+      pll_ref_clk     => PllRefClk,
+      rfdc_clk        => RfdcClk,
+      sysref_in       => sysref_in,
+      enable_rclk     => enable_rclk,
+      sysref_out_pclk => sysref_out_pclk,
+      sysref_out_rclk => sysref_out_rclk
+    );
+
+  main: process
+  begin
+    enable_rclk <= '1';
+    ClkWait(100);
+    wait until falling_edge(sysref_out_rclk);
+    ClkWait;
+    wait until falling_edge(RfdcClk);
+    enable_rclk <= '0';
+    ClkWait(100);
+    wait until falling_edge(RfdcClk);
+    enable_rclk <= '1';
+    ClkWait(100);
+
+    StopSim <= true;
+    wait;
+  end process;
+
+  sysref: process(PllRefClk)
+    variable count : integer := 1;
+  begin
+    if rising_edge(PllRefClk) then
+      count := count +1;
+      if count = 10 then
+        sysref_in <= not sysref_in;
+        count := 1;
+      end if;
+    end if;
+  end process;
+
+  checker_pll_ref_clk: process(PllRefClk)
+  begin
+    if falling_edge(PllRefClk) then
+      SysrefDly    <= sysref_in;
+      SysrefDlyDly <= SysrefDly;
+      assert SysrefDlyDly = sysref_out_pclk
+        report "SYSREF incorrectly captured in the PllRefClk domain"
+        severity error;
+    end if;
+  end process;
+
+  checker_rfdc_clk: process(RfdcClk)
+  begin
+    if falling_edge(RfdcClk) then
+      rSysref    <= sysref_out_pclk;
+      assert (rSysref = sysref_out_rclk) or (enable_rclk = '0')
+        report "SYSREF incorrectly captured in the RfdcClk domain."
+        severity error;
+    end if;
+  end process;
+
+end RTL;