Clarify g_nof_destinations_max design revision parameter and package constants...

Clarify g_nof_destinations_max design revision parameter and package constants c_sdp_bdo_mm_nof_destinations_max = 32 and c_sdp_bdo_reorder_nof_blocks_max = 16.

Closes L2SDP-964

applications/lofar2/libraries/sdp/src/vhdl/sdp_bdo_pkg.vhd

@@ -110,15 +110,26 @@ end package sdp_bdo_pkg;
 
 package body sdp_bdo_pkg is
   function func_sdp_bdo_parse_nof_destinations(nof_destinations, c_nof_destinations_max : natural) return natural is
+    constant c_last_arr : t_natural_arr(1 to c_nof_destinations_max) :=
+                            func_sdp_bdo_nof_beamlets_per_block_last_destination_look_up_table(c_nof_destinations_max);
+    variable v_DN       : natural := 1;
   begin
     -- Parse input nof_destinations value
     if nof_destinations = 0 then
-      return 1;
+      v_DN := 1;  -- force to at least 1 destination
     elsif nof_destinations > c_nof_destinations_max then
-      return c_nof_destinations_max;
+      v_DN := c_nof_destinations_max;
     else
-      return nof_destinations;
+      v_DN := nof_destinations;
     end if;
+    -- Check whether nof beamlet indices can be distributed over v_DN
+    -- destinations, else force to use one less destination, see
+    -- func_sdp_bdo_nof_beamlets_per_block_last_destination_look_up_table()
+    -- description for further explanation.
+    if c_last_arr(v_DN) = 0 then
+      v_DN := v_DN - 1;
+    end if;
+    return v_DN;
   end func_sdp_bdo_parse_nof_destinations;
 
   function func_sdp_bdo_reorder_nof_blocks_look_up_table(c_nof_destinations_max : natural) return t_natural_arr is
@@ -179,6 +190,7 @@ package body sdp_bdo_pkg is
     variable v_first_arr : t_natural_arr(1 to c_nof_destinations_max) :=
                              func_sdp_bdo_nof_beamlets_per_block_first_destinations_look_up_table(c_nof_destinations_max);
     variable v_last_arr  : t_natural_arr(1 to c_nof_destinations_max);
+    variable v_last      : integer;
   begin
     -- Determine remaining nof_beamlets_per_block for the last destination
     -- with index DN, as function of number of destinations DN.
@@ -188,17 +200,30 @@ package body sdp_bdo_pkg is
     --     DN = 1:16 --> v_first_arr = 488, 244, 163, 122, 98, 82, 70, 61, 55, 49, 45, 41, 38, 35, 33, 31
     --     DN = 1:16 --> v_last_arr  = 488, 244, 162, 122, 96, 78, 68, 61, 48, 47, 38, 37, 32, 33, 26, 23
     --
+    --     DN = 17:32 --> v_first_arr = 29, 28, 26, 25, 24, 23, 22, 21, 20, 19, 19, 18, 17, 17, 16, 16
+    --     DN = 17:32 --> v_last_arr  = 24, 12, 20, 13,  8,  5,  4,  5,  8, 13, -6,  2, 12, -5,  8, -8
+    --                                                                          27,         30,     32
     -- Remark:
-    -- . The v_last_arr(DN) may be < v_first_arr(DN) - 1, so the last
-    --   destination may contain much less beamlets than the others. In
-    --   combination with dp_packet_unmerge it is not feasible to distribute
-    --   the beamlets evenly over all destinations, using v_hi beamlets for
-    --   some first destinations and v_lo = v_hi - 1 for the remaining
-    --   destinations. This is because dp_packet_unmerge can only unmerge the
-    --   same packet length for N - 1 blocks and then unmerge the remaining
-    --   data in the last block until the eop.
+    -- . The v_last_arr(DN) <= v_first_arr(DN), because dp_packet_unmerge
+    --   can only unmerge the same packet length for N - 1 blocks and then
+    --   unmerge the remaining data in the last block until the input eop.
+    -- . The v_last_arr(DN) can be < v_first_arr(DN) - 1, so the last
+    --   destination then contains much less beamlets than the others.
+    -- . In combination with dp_packet_unmerge it is not feasible to
+    --   distribute the beamlets evenly over all destinations, using v_first
+    --   beamlets for some first destinations and v_first - 1 beamlets for
+    --   the remaining destinations.
+    -- . The v_last must be > 0. Therefor some number of destinations are
+    --   not possible in combination with c_sdp_S_sub_bf = 488. From the
+    --   v_last_arr it follows that DN = 27, 30 and 32 are not possible for
+    --   multiple destination BDO.
     for DN in 1 to c_nof_destinations_max loop
-      v_last_arr(DN) := c_sdp_S_sub_bf - (DN - 1) * v_first_arr(DN);
+      v_last := c_sdp_S_sub_bf - (DN - 1) * v_first_arr(DN);
+      if v_last > 0 then
+        v_last_arr(DN) := v_last;
+      else
+        v_last_arr(DN) := 0;  -- force 0 to fit in natural
+      end if;
     end loop;
     return v_last_arr;
   end func_sdp_bdo_nof_beamlets_per_block_last_destination_look_up_table;
@@ -213,10 +238,17 @@ package body sdp_bdo_pkg is
     -- Determine nof_ch per packet for the first 1:DN-1 destinations, as
     -- function of number of destinations DN.
     -- The packet lengths follow from c_nof_blocks_arr * c_nof_beamlets_arr:
+    --                   DN =    1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,  16
     -- . c_nof_blocks_arr   =    4,   8,  12,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16
     -- . c_nof_beamlets_arr =  488, 244, 163, 122,  98,  82,  70,  61,  55,  49,  45,  41,  38,  35,  33,  31
     -- . v_len_arr          = 1952,1952,1956,1952,1568,1312,1120, 976, 880, 784, 720, 656, 608, 560, 528, 496
     -- . nof octets         = 7808,7808,7824,7808,6272,5248,4480,3904,3520,3136,2880,2624,2432,2240,2112,1984
+    --
+    --                   DN =   17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,  30,  31,  32
+    -- . c_nof_blocks_arr   =   16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16,  16
+    -- . c_nof_beamlets_arr =   29,  28,  26,  25,  24,  23,  22,  21,  20,  19,  19,  18,  17,  17,  16,  16
+    -- . v_len_arr          =  464, 448, 416, 400, 384, 368, 352, 336, 320, 304, 304, 288, 272, 272, 256, 256
+    -- . nof octets         = 1856,1792,1664,1600,1536,1472,1408,1344,1280,1216,1216,1152,1088,1088,1024,1024
     for DN in 1 to c_nof_destinations_max loop
       v_len_arr(DN) := c_nof_blocks_arr(DN) * c_nof_beamlets_arr(DN);
     end loop;