Support g_fifo_af_xon

libraries/base/dp/src/vhdl/dp_mux.vhd

@@ -105,7 +105,8 @@ ENTITY dp_mux IS
     g_use_in_channel    : BOOLEAN := FALSE;
     g_use_error         : BOOLEAN := FALSE;
     g_use_sync          : BOOLEAN := FALSE;
-    g_fifo_af_margin    : NATURAL := 4;  -- Nof words below max (full) at which fifo is considered almost full
+    g_fifo_af_margin    : NATURAL := 4;  -- >=4, Nof words below max (full) at which fifo is considered almost full for snk_out.ready
+    g_fifo_af_xon       : NATURAL := 0;  -- >=0, Nof words below max (full) at which fifo is considered almost full for snk_out.xon
     g_fifo_size         : t_natural_arr := array_init(1024, 2);  -- must match g_nof_input, even when g_use_fifo=FALSE
     g_fifo_fill         : t_natural_arr := array_init(   0, 2)   -- must match g_nof_input, even when g_use_fifo=FALSE
   ); 
@@ -229,6 +230,7 @@ BEGIN
         g_fifo_fill      => c_fifo_fill(I),
         g_fifo_size      => c_fifo_size(I),
         g_fifo_af_margin => g_fifo_af_margin,
+        g_fifo_af_xon    => g_fifo_af_xon,
         g_fifo_rl        => 1
       )
       PORT MAP (