2 files changed, 21 insertions(+), 9 deletions(-)

M src/data_link/frame_alignment.vhd
M testbench/data_link/frame_alignment_tb.vhd

@@ 79,6 79,7 @@ architecture a1 of frame_alignment is
   signal reg_known_sync_char_position : integer range 0 to 256;
 
   signal next_octet_index : integer := 0;
+  signal next_adjusted_octet_index : integer := 0;
 begin  -- architecture a1
   data_buffer: entity work.ring_buffer
     generic map (


@@ 117,6 118,7 @@ begin  -- architecture a1
       reg_state <= INIT;
       reg_last_frame_data <= (others => '0');
       next_frame_state <= ('0', '0', '0', '0', '0', '0', '0', '0');
+      buffer_align_to <= -1;
     elsif ci_char_clk'event and ci_char_clk = '1' then  -- rising clock edge
       -- set last_frame_data if this is the last frame and not /F/ or /A/
       if next_is_last_octet = '1' and not (is_f = '1' or is_a = '1') then


@@ 169,7 171,7 @@ begin  -- architecture a1
             reg_state <= ALIGNED;
           elsif ci_realign = '1' then
             -- align to last known sync char position
-            buffer_align_to <= reg_known_sync_char_position;
+            buffer_align_to <= reg_known_sync_char_position + buffer_read_position;
             reg_state <= ALIGNED;
           end if;
         end if;


@@ 179,17 181,18 @@ begin  -- architecture a1
 
   co_correct_sync_chars <= reg_correct_sync_chars;
   buffer_raw_adjust_position <= (buffer_align_to + 1 - buffer_read_position) mod F;
-  buffer_adjust_position <= buffer_raw_adjust_position when buffer_raw_adjust_position < F/2 + 1
+  buffer_adjust_position <= buffer_raw_adjust_position when buffer_raw_adjust_position <= F/2 + 1
                             else buffer_raw_adjust_position - F;
 
   is_wrong_char <= (is_f and not next_is_last_octet) or (is_a and not next_is_last_octet);
   buffer_character <= di_char.d8b when is_f = '0' and is_a = '0' else
-                 reg_last_frame_data when SCRAMBLED else
+                 reg_last_frame_data when not SCRAMBLED else
                  F_replace_data when is_f = '1' else
                  A_replace_data;
 
-  next_octet_index <= buffer_write_position mod F;
-  next_is_last_octet <= '1' when F = 1 or next_octet_index = F - 2 else '0';
+  next_adjusted_octet_index <= (buffer_write_position - buffer_read_position - buffer_adjust_position) mod F;
+  next_octet_index <= (buffer_write_position - buffer_read_position) mod F;
+  next_is_last_octet <= '1' when next_adjusted_octet_index = F - 1 else '0';
 
   is_f <= '1' when di_char.d8b = F_char and di_char.kout = '1' else '0';
   is_a <= '1' when di_char.d8b = A_char and di_char.kout = '1' else '0';

@@ 38,7 38,7 @@ architecture a1 of frame_alignment_tb is
     ('0', '0', ('1', '0', '0', "00000010", '1'), '1', '0'),
     ('0', '0', ('0', '0', '0', "00000011", '1'), '1', '0'),
     ('0', '0', ('0', '0', '0', "00000100", '1'), '1', '0'),
-    ('0', '0', ('0', '0', '0', "00000000", '1'), '1', '0'),  -- frame begins
+    ('0', '0', ('0', '0', '0', "00000000", '1'), '1', '0'),  -- frame ends
     ('0', '0', ('1', '0', '0', "11111100", '1'), '0', '1'),  -- frame begins, /A/
     ('0', '0', ('1', '0', '0', "11111100", '1'), '0', '1'),  -- frame begins, /A/
     ('0', '0', ('0', '0', '0', "01000001", '1'), '0', '1'),


@@ 50,9 50,18 @@ architecture a1 of frame_alignment_tb is
     ('0', '0', ('0', '0', '0', "00100010", '1'), '1', '0'),
     ('0', '0', ('0', '0', '0', "00100011", '1'), '1', '0'),
     ('0', '0', ('0', '0', '0', "00100100", '1'), '1', '0'),
-    ('0', '0', ('0', '0', '0', "00000101", '1'), '1', '0'),
-    ('0', '0', ('0', '0', '0', "00000001", '1'), '1', '0'),
-    ('0', '0', ('0', '0', '0', "00000000", '1'), '1', '0')  -- frame begin
+    ('0', '0', ('0', '0', '0', "10000101", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "01000001", '1'), '1', '0'), -- frame begins
+    ('0', '0', ('0', '0', '0', "01000010", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "01000011", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "01000100", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "01000101", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "00100001", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "00100010", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "00100011", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "00100100", '1'), '1', '0'),
+    ('0', '0', ('1', '0', '0', "11111100", '1'), '1', '0'),
+    ('0', '0', ('0', '0', '0', "00000000", '1'), '1', '0')
   );
 
   constant char_clk_period : time := 1 ns;