Resolve L2SDP-557

Closes L2SDP-557

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

@@ -133,7 +133,6 @@ BEGIN
     );
 
   -- discarded counter
-  cnt_discarded_en <= '1' WHEN in_sosi.sync = '1' AND bsn_ok = '0' ELSE '0';
   u_discarded_counter : ENTITY common_lib.common_counter
   GENERIC MAP (
     g_width => c_word_w,
@@ -187,16 +186,55 @@ BEGIN
     -- MM registers in st_clk domain
     reg_wr_arr  => OPEN,
     reg_rd_arr  => OPEN,
-    in_reg      => count_reg,   -- read only
+    in_reg      => count_reg, -- read only
     out_reg     => OPEN       -- no write
   );
 
-  bsn_at_sync <= bs_sosi.bsn WHEN bs_sosi.sync = '1' ELSE bsn_at_sync_reg;
-  bsn_ok      <= bsn_ok_reg WHEN in_sosi.sync = '0' ELSE '1' WHEN in_sosi.bsn = bsn_at_sync ELSE '0';
-  out_valid   <= '1'    WHEN in_sosi.sop = '1' AND TO_UINT(in_sosi.channel) /= g_check_channel ELSE
-                 bsn_ok WHEN in_sosi.sop = '1' AND TO_UINT(in_sosi.channel) = g_check_channel ELSE
-                 out_valid_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;
+    -- 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;
+    out_valid        <= out_valid_reg;
+    cnt_discarded_en <= '0'; 
+
+    IF bs_sosi.sync = '1' THEN
+      v_bsn_at_sync := bs_sosi.bsn(g_bsn_w-1 DOWNTO 0);
+    END IF;
+
+    IF TO_UINT(in_sosi.channel) = g_check_channel THEN 
+      IF in_sosi.sync = '1' THEN 
+        -- Compare bsn at sync of in_sosi to bsn at sync of bs_sosi.
+        IF UNSIGNED(in_sosi.bsn(g_bsn_w-1 DOWNTO 0)) = UNSIGNED(v_bsn_at_sync) THEN
+          v_bsn_ok := '1';
+        ELSE
+          v_bsn_ok := '0';
+        END IF;
+
+        -- set cnt_discarded_en to control u_discarded_counter.  
+        cnt_discarded_en <= NOT v_bsn_ok;
+      END IF;
 
+      -- Setting out_valid to control the discarding at packet level.
+      IF in_sosi.sop = '1' THEN
+        out_valid <= v_bsn_ok;
+      END IF;
+    ELSE
+      IF in_sosi.sop = '1' THEN
+        out_valid <= '1'; -- Packets with channel unequal to g_check_channel are always valid
+      END IF;
+
+    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)
   BEGIN
     IF dp_rst='1' THEN