phy: rx: Come up in disconnected state after reset

trashernet/trashernet_phy.vhd

@@ -37,9 +37,10 @@ begin
 
 	receiver : block
 		-- Signal conditioning
-		signal rx      : std_logic;
-		signal rx_last : std_logic;
-		signal rx_edge : std_logic;
+		signal rx             : std_logic;
+		signal rx_last        : std_logic;
+		signal rx_last_static : std_logic;
+		signal rx_edge        : std_logic;
 
 		-- Bit recovery
 		signal bit_value : std_logic;
@@ -61,11 +62,23 @@ begin
 				data_out => rx
 			);
 
-		-- Edge detector for RX
-		rx_last <= '0' when rst
-		           else rx when rising_edge(clk)
-		         ;
-		rx_edge <= rx_last xor rx;
+		-- Edge detector for RX (+glitch filter)
+		edgedet : process(clk, rst) is
+		begin
+			if rst then
+				rx_last        <= '0';
+				rx_last_static <= '0';
+				rx_edge        <= '0';
+
+			elsif rising_edge(clk) then
+				rx_edge <= '0';
+				if (rx_last = rx) then
+					rx_edge        <= rx_last_static xor rx;
+					rx_last_static <= rx;
+				end if;
+				rx_last <= rx;
+			end if;
+		end process edgedet;
 
 		demanchestizer : block
 			-- Transition detector
@@ -85,7 +98,7 @@ begin
 			signal bit_ev          : bit_ev_t;
 
 			-- Bit recovery
-			type demanchestization_state_t is (SYNC, DATA);
+			type demanchestization_state_t is (SYNC, DATA, ERROR);
 			signal demanchestization_state : demanchestization_state_t;
 		begin
 			-- Detects spacing of transitions
@@ -133,7 +146,7 @@ begin
 
 					if transition_stb then
 						case last_transition is
-							when LONG =>
+							when LONG => -- @suppress: Exit condition through indirect assignment
 								if transition_duration = LONG then
 									bit_ev <= TOGGLE;
 								end if;
@@ -147,6 +160,10 @@ begin
 								last_transition <= LONG;
 						end case;
 					end if;
+
+					if (not transition_activity) then
+						last_transition <= LONG;
+					end if;
 				end if;
 			end process transition_analyzer;
 
@@ -157,23 +174,32 @@ begin
 					demanchestization_state <= SYNC;
 					bit_stb                 <= '0';
 					rx_active               <= '0';
-
+					rx_error                <= '0';
 				elsif rising_edge(clk) then
-					bit_stb <= '0';
+					bit_stb  <= '0';
+					rx_error <= '0';
+
 					if (bit_ev /= NONE) then
-						rx_active <= '1';
 						case demanchestization_state is
 							when SYNC =>
 								if (bit_ev = KEEP) then
 									bit_value               <= '1';
 									demanchestization_state <= DATA;
+									rx_active               <= '1';
 								end if;
-							when DATA =>
+							when DATA => -- @suppress: Condition outside of case allows to exit this state
 								bit_value <= not bit_value when bit_ev = TOGGLE else bit_value;
 								bit_stb   <= '1';
+							when ERROR => -- @suppress: Condition outside of case allows to exit this state
+								null;
 						end case;
 					end if;
 
+					if (bit_ev = ERROR) then
+						rx_error                <= '1';
+						demanchestization_state <= ERROR;
+					end if;
+
 					if (not transition_activity) then
 						demanchestization_state <= SYNC;
 						rx_active               <= '0';
@@ -194,7 +220,7 @@ begin
 
 				if rx_active then
 					if (bit_stb) then
-						data_rx <= data_rx(data_rx'high - 1 downto 0) & bit_value;
+						data_rx <= bit_value & data_rx(data_rx'high downto data_rx'low + 1);
 						if (bit_cnt = 7) then
 							data_rx_valid <= '1';
 							bit_cnt       <= 0;
@@ -212,7 +238,7 @@ begin
 		nlp_timeout_p : process(clk, rst) is
 		begin
 			if rst then
-				nlp_timeout_cnt <= NLP_TIMEOUT_CNT_MAX;
+				nlp_timeout_cnt <= 0;
 			elsif rising_edge(clk) then
 				if rx_edge then         -- Technically, we should use only the rising edge here, but a project called `trashernet` probably won't mind ;)
 					nlp_timeout_cnt <= NLP_TIMEOUT_CNT_MAX;
@@ -244,5 +270,4 @@ begin
 		end process nlp;
 		tx_p <= '1' when cnt < 0 else '0';
 	end block transmitter;
-
 end architecture rtl;