processed review comments

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

@@ -190,9 +190,14 @@ BEGIN
     out_reg     => OPEN       -- no write
   );
 
-  p_bsn_check : PROCESS(bs_sosi, in_sosi, bsn_at_sync_reg, bsn_ok_reg)
+  -- Process to check the bsn at sync. It captures the bsn at the sync of bs_sosi. Then compares that bsn to
+  -- the bsn at sync of in_sosi. If they are unequal all packets during that sync period with in_sosi.channel 
+  -- equal to g_check_channel are discarded.
+  p_bsn_check : PROCESS(bs_sosi, in_sosi, bsn_at_sync_reg, bsn_ok_reg, out_valid_reg)
+    -- v_bsn_ok used for the first in_sosi packet of a sync period as sync and sop are both '1'.
     VARIABLE v_bsn_ok      : STD_LOGIC;
-    VARIABLE v_bsn_at_sync : STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0);  
+    -- Using v_bsn_at_sync to ensure correct behavior when in_sosi has no latency compared to bs_sosi.
+    VARIABLE v_bsn_at_sync : STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0); 
   BEGIN
     v_bsn_at_sync := bsn_at_sync_reg;     
     v_bsn_ok      := bsn_ok_reg;
@@ -202,30 +207,32 @@ BEGIN
       v_bsn_at_sync := bs_sosi.bsn;
     END IF;
 
-    IF in_sosi.sync = '1' AND TO_UINT(in_sosi.channel) = g_check_channel THEN 
-      IF in_sosi.bsn = v_bsn_at_sync THEN
-        v_bsn_ok := '1';
-      ELSE
-        v_bsn_ok := '0';
+    IF TO_UINT(in_sosi.channel) = g_check_channel THEN 
+      -- Compare bsn at sync of in_sosi to bsn at sync of bs_sosi.
+      IF in_sosi.sync = '1' THEN 
+        IF in_sosi.bsn = v_bsn_at_sync THEN
+          v_bsn_ok := '1';
+        ELSE
+          v_bsn_ok := '0';
+        END IF;
       END IF;
-    END IF;
 
-    IF in_sosi.sop = '1' THEN
-      IF TO_UINT(in_sosi.channel) = g_check_channel THEN
+      -- Setting out_valid to control the discarding at packet level.
+      IF in_sosi.sop = '1' THEN
         out_valid <= v_bsn_ok;
-      ELSE
-        out_valid <= '1';
       END IF;
-    END IF;
- 
-    IF TO_UINT(in_sosi.channel) = g_check_channel THEN
+
+      -- set cnt_discarded_en to control u_discarded_counter.  
       cnt_discarded_en <= in_sosi.sync AND NOT v_bsn_ok;
     ELSE
-      cnt_discarded_en <= '0';
-    END IF;
+      IF in_sosi.sop = '1' THEN
+        out_valid <= '1'; -- Packets with channel unequal to g_check_channel are always valid
+      END IF;
 
-    bsn_ok      <= v_bsn_ok;
-    bsn_at_sync <= v_bsn_at_sync;
+      cnt_discarded_en <= '0'; -- Packets with channel unequal to g_check_channel cannot be discarded.
+    END IF;
+    bsn_ok      <= v_bsn_ok;      -- bsn_ok is used to indicate if the bsn is correct for the entire sync period of g_check_channel.
+    bsn_at_sync <= v_bsn_at_sync; -- register to store the bsn at sync of bs_sosi.
   END PROCESS;
   
   p_dp_clk : PROCESS(dp_rst, dp_clk)

libraries/base/dp/tb/vhdl/tb_dp_block_validate_bsn_at_sync.vhd

@@ -63,7 +63,8 @@ ARCHITECTURE tb OF tb_dp_block_validate_bsn_at_sync IS
   CONSTANT c_gap_size       : NATURAL := 4;
   CONSTANT c_nof_sync       : NATURAL := 5;
   CONSTANT c_nof_blk        : NATURAL := g_nof_blocks_per_sync * c_nof_sync;
-  CONSTANT c_check_channel  : NATURAL := g_nof_blocks_per_sync;
+  -- choosing c_check_channel such that it corresponds with a channel from stimuli on a sync because the channel field is generated by a counter.
+  CONSTANT c_check_channel  : NATURAL := g_nof_blocks_per_sync; -- can be c_check_channel MOD g_nof_blocks_per_sync = 0 but not larger than c_nof_blk.
   
   SIGNAL dp_clk             : STD_LOGIC := '1';
   SIGNAL mm_clk             : STD_LOGIC := '1';
@@ -191,7 +192,8 @@ BEGIN
   VARIABLE v_valid_blk : BOOLEAN := TRUE;
   BEGIN
     IF rising_edge(dp_clk) THEN
-      IF reference_sosi.sop = '1' THEN
+      IF reference_sosi.sop = '1' THEN --Decide for each block if it should be valid.
+        -- A block can only be discarded if its channel field corresponds with the check_channel.
         IF g_bsn_init >= g_nof_blocks_per_sync AND TO_UINT(reference_sosi.channel) = c_check_channel THEN
           v_valid_blk := FALSE;
         ELSE