src: Implement protocol exception in Protocol control FSM.

src/can_core/protocol_control.vhd

@@ -456,6 +456,8 @@ architecture rtl of protocol_control is
   -- Secondary sampling point configuration
   signal drv_ssp_delay_select     :     std_logic_vector(1 downto 0);
   
+  -- Protocol exception
+  signal drv_pex                  :     std_logic;
   
   -----------------------------------------------------------------------------
   -- Internal signals
@@ -626,6 +628,7 @@ begin
     drv_bus_off_reset     <=  drv_bus(DRV_ERR_CTR_CLR);
     drv_ssp_delay_select  <=  drv_bus(DRV_SSP_DELAY_SELECT_HIGH downto
                                       DRV_SSP_DELAY_SELECT_LOW);
+    drv_pex               <=  drv_bus(DRV_PEX_INDEX);
   
     ---------------------------------------------------------------------------
     -- TX Data word endian swapper
@@ -668,6 +671,7 @@ begin
         drv_int_loopback_ena    => drv_int_loopback_ena,-- IN
         drv_can_fd_ena          => drv_can_fd_ena,      -- IN
         drv_ssp_delay_select    => drv_ssp_delay_select,-- IN
+        drv_pex                 => drv_pex,             -- IN
         is_control              => is_control,          -- OUT
         is_data                 => is_data,             -- OUT
         is_stuff_count          => is_stuff_count,      -- OUT

src/can_core/protocol_control_fsm.vhd

@@ -138,6 +138,9 @@ entity protocol_control_fsm is
         -- Secondary sampling point delay select
         drv_ssp_delay_select    :in   std_logic_vector(1 downto 0);
         
+        -- Protocol exception handling
+        drv_pex                 :in   std_logic;
+        
         -- Control field is being transmitted
         is_control              :out  std_logic;
 
@@ -746,6 +749,10 @@ architecture rtl of protocol_control_fsm is
     -- Clear bus-off reset flag
     signal clr_bus_off_rst_flg       :  std_logic;
     
+    -- Protocol exception signals
+    signal pex_on_fdf_enable         :  std_logic;
+    signal pex_on_res_enable         :  std_logic;
+    
 begin
 
     tx_frame_ready <= '1' when (tran_frame_valid = '1' and drv_bus_mon_ena = '0')
@@ -821,6 +828,16 @@ begin
                              else
                          '0';
 
+    pex_on_fdf_enable <= '1' when (drv_ena = FDE_DISABLE and
+                                   drv_pex = PROTOCOL_EXCEPTION_ENABLED) 
+                             else
+                         '0';
+
+    pex_on_res_enable <= '1' when (drv_ena = FDE_ENABLE and
+                                   drv_pex = PROTOCOL_EXCEPTION_ENABLED)
+                             else
+                         '0';
+
     ---------------------------------------------------------------------------
     -- CRC sequence selection
     ---------------------------------------------------------------------------
@@ -1000,9 +1017,13 @@ begin
             when s_pc_edl_r1 =>
                 if (rx_data_nbs = DOMINANT) then
                     next_state <= s_pc_r0_ext;
+                else
+                    if (pex_on_fdf_enable = '1') then
+                        next_state <= s_pc_integrating;
                     else
                         next_state <= s_pc_r0_fd;
                     end if; 
+                end if;
                     
             -------------------------------------------------------------------
             -- r0 bit after EDL/r1 bit in Extended CAN Frames.
@@ -1011,10 +1032,14 @@ begin
                 next_state <= s_pc_dlc;
 
             -------------------------------------------------------------------
-            -- r0 bit in CAN FD Frames (both Base and Extended identifier)
+            -- r0(res) bit in CAN FD Frames (both Base and Extended identifier)
             ------------------------------------------------------------------- 
             when s_pc_r0_fd =>
+                if (rx_data_nbs = RECESSIVE and pex_on_res_enable = '1') then
+                    next_state <= s_pc_integrating;
+                else
                     next_state <= s_pc_brs;
+                end if;    
                 
             -------------------------------------------------------------------
             -- EDL/r0 bit in CAN 2.0 and CAN FD Frames with BASE identifier
@@ -1023,9 +1048,15 @@ begin
             when s_pc_edl_r0 =>
                 if (rx_data_nbs = DOMINANT) then
                     next_state <= s_pc_dlc;
+                else
+                    -- Protocol exception on recessive FDF/EDL in "Classical CAN"
+                    -- configuration
+                    if (pex_on_fdf_enable = '1') then
+                        next_state <= s_pc_integrating;
                     else
                         next_state <= s_pc_r0_fd;
                     end if;
+                end if; 
             
             -------------------------------------------------------------------
             -- BRS (Bit rate shift) Bit
@@ -1746,11 +1777,29 @@ begin
                     end if;
                 end if;
                 
-                if ((drv_can_fd_ena = FDE_DISABLE) or
-                    (tran_frame_type = NORMAL_CAN and is_transmitter = '1'))
-                    and (rx_data_nbs = RECESSIVE)
+                -- Sample recessive but CAN FD is disabled -> Form error or
+                -- protocol exception!
+                if (rx_data_nbs = RECESSIVE and
+                    drv_can_fd_ena = FDE_DISABLE)
                 then
+                    if (drv_pex = PROTOCOL_EXCEPTION_DISABLED) then
                         form_err_i <= '1';
+                    
+                    -----------------------------------------------------------
+                    -- Here we detect protocol exception. Although unit should
+                    -- not be transmitter at this moment (see datasheet), it
+                    -- is possible user is stupid! Unlock TXT Buffer so that
+                    -- it does not end up in deadlock!
+                    -----------------------------------------------------------
+                    elsif (is_transmitter = '1') then
+                        txtb_hw_cmd_d.unlock <= '1';
+                        stuff_enable_clear <= '1';
+                        if (tx_failed = '1') then
+                            txtb_hw_cmd_d.failed  <= '1';
+                        else
+                            txtb_hw_cmd_d.arbl    <= '1';
+                        end if;
+                    end if;
                 end if;
 
             -------------------------------------------------------------------
@@ -1793,7 +1842,24 @@ begin
                 -- protocol (CAN XL in future). Now we don't have protocol
                 -- exception, so we throw error here!
                 if (rx_data_nbs = RECESSIVE) then
+                    if (drv_pex = PROTOCOL_EXCEPTION_DISABLED) then
                         form_err_i <= '1';
+
+                    -----------------------------------------------------------
+                    -- Here we detect protocol exception. Although unit should
+                    -- not be transmitter at this moment (see datasheet), it
+                    -- is possible user is stupid! Unlock TXT Buffer so that
+                    -- it does not end up in deadlock!
+                    -----------------------------------------------------------
+                    elsif (is_transmitter = '1') then
+                        txtb_hw_cmd_d.unlock <= '1';
+                        stuff_enable_clear <= '1';
+                        if (tx_failed = '1') then
+                            txtb_hw_cmd_d.failed  <= '1';
+                        else
+                            txtb_hw_cmd_d.arbl    <= '1';
+                        end if;
+                    end if;
                 end if;
                 
             -------------------------------------------------------------------
@@ -1821,11 +1887,29 @@ begin
                     ssp_reset_i <= '1';
                 end if;
                 
-                if ((drv_can_fd_ena = FDE_DISABLE) or
-                    (tran_frame_type = NORMAL_CAN and is_transmitter = '1'))
-                    and (rx_data_nbs = RECESSIVE)
+                -- Sample recessive but CAN FD is disabled -> Form error or
+                -- protocol exception!
+                if (rx_data_nbs = RECESSIVE and
+                    drv_can_fd_ena = FDE_DISABLE)
                 then
+                    if (drv_pex = PROTOCOL_EXCEPTION_DISABLED) then
                         form_err_i <= '1';
+
+                    -----------------------------------------------------------
+                    -- Here we detect protocol exception. Although unit should
+                    -- not be transmitter at this moment (see datasheet), it
+                    -- is possible user is stupid! Unlock TXT Buffer so that
+                    -- it does not end up in deadlock!
+                    -----------------------------------------------------------
+                    elsif (is_transmitter = '1') then
+                        txtb_hw_cmd_d.unlock <= '1';
+                        stuff_enable_clear <= '1';
+                        if (tx_failed = '1') then
+                            txtb_hw_cmd_d.failed  <= '1';
+                        else
+                            txtb_hw_cmd_d.arbl    <= '1';
+                        end if;
+                    end if;
                 end if;
 
             -------------------------------------------------------------------

src/lib/can_components.vhd

@@ -1520,6 +1520,9 @@ package can_components is
         -- Secondary sampling point delay select
         drv_ssp_delay_select    :in   std_logic_vector(1 downto 0);
         
+        -- Protocol exception handling
+        drv_pex                 :in   std_logic;
+        
         -- Arbitration field is being transmitted
         is_arbitration          :out  std_logic;
         

src/lib/drv_stat_pkg.vhd

@@ -218,6 +218,8 @@ package drv_stat_pkg is
     constant DRV_ENA_INDEX     : natural := 509;
     constant DRV_FD_TYPE_INDEX : natural := 510;
     
+    constant DRV_PEX_INDEX     : natural := 511;
+
     ----------------------------------------------------------------------------
     -- RX, TX and TXT Buffer frame format signal indexes
     ----------------------------------------------------------------------------

src/memory_registers/memory_registers.vhd

@@ -592,6 +592,9 @@ begin
     drv_bus(DRV_INT_LOOBACK_ENA_INDEX) <= align_wrd_to_reg(
         control_registers_out.settings, ILBP_IND);
 
+    -- PEX - Protocol exception mode
+    drv_bus(DRV_PEX_INDEX) <= align_wrd_to_reg(
+        control_registers_out.settings, PEX_IND);
 
     ---------------------------------------------------------------------------
     -- INT_STAT - Clearing interrupt vector by write
@@ -1424,14 +1427,13 @@ begin
     drv_bus(360 downto 358) <= (OTHERS => '0');
     drv_bus(362 downto 361) <= (OTHERS => '0');
     drv_bus(365 downto 363) <= (OTHERS => '0');
-    drv_bus(370 downto 368) <= (OTHERS => '0');
-    drv_bus(371)            <= '0';
+    drv_bus(371 downto 368) <= (OTHERS => '0');
     drv_bus(399 downto 383) <= (OTHERS => '0');
     drv_bus(459 downto 445) <= (OTHERS => '0');
     drv_bus(464 downto 462) <= (OTHERS => '0');
     drv_bus(609 downto 601) <= (OTHERS => '0');
     drv_bus(579 downto 570) <= (OTHERS => '0');
-    drv_bus(519 downto 511) <= (OTHERS => '0');
+    drv_bus(519 downto 512) <= (OTHERS => '0');
     drv_bus(506 downto 475) <= (OTHERS => '0');
     drv_bus(444 downto 430) <= (OTHERS => '0');