history/display: backspace logic

[hwmod.git] / src / uart_tx.vhd

diff --git a/src/uart_tx.vhd b/src/uart_tx.vhd
index 7d06e4cdef757d6597f317bd1cab6a4c02bcee2a..f3ccc8f4e584bc4bdfbe0aea7793a77e7200379e 100644 (file)
--- a/src/uart_tx.vhd
+++ b/src/uart_tx.vhd
@@ -12,8 +12,8 @@ entity uart_tx is
 port(
        sys_clk : in std_logic;
        sys_res : in std_logic;
-       --txd : out std_logic;
-       --tx_data : in std_logic;
+       txd : out std_logic;
+       tx_data : in std_logic_vector(7 downto 0); -- map this to a larger register with containing input
        tx_new : in std_logic;
        tx_done : out std_logic
 );
@@ -23,32 +23,81 @@ architecture beh of uart_tx is
        signal timer : integer range 0 to 65535;
        signal timer_next : integer range 0 to 65535;
        constant timer_max : integer := 35;
-       signal counter : integer;
-       signal counter_next : integer;
+       signal counter : integer range 0 to 15;
+       signal counter_next : integer range 0 to 15;
+       signal txd_next : std_logic;
 begin
        process (sys_clk, sys_res)
        begin
                if sys_res = '0' then
                        counter <= 0;
                        timer <= 0;
+                       txd <= '0';
+                       txd_next <= '0';
                elsif rising_edge(sys_clk) then
                        counter <= counter_next;
                        timer <= timer_next;
+                       txd <= txd_next;
                end if;
        end process;
 
-
-       process (timer, counter)
+       process(timer)
        begin
                if (timer = timer_max) then
                        timer_next <= 0;
-                       counter_next <= counter + 1;
                else
                        timer_next <= timer + 1;
-                       counter_next <= counter;
                end if;
        end process;
 
+       process (timer, counter, tx_new)
+       begin
+               if (tx_new = '1') then
+                       if (timer = timer_max) then
+                               if (counter > 10) then
+                                       counter_next <= 0;
+                               else
+                                       counter_next <= counter + 1;
+                               end if;
+                       else
+                                       counter_next <= counter;
+                       end if;
+               else
+                               counter_next <= 0;
+               end if;
+       end process;
+
+       process (counter)
+       begin
+               -- TODO: this is always 8N1 and anything but optimal
+               case (counter) is 
+                       when 0 =>
+                               txd_next <= '1';
+                       when 1 =>
+                               txd_next <= tx_data(0);
+                       when 2 =>
+                               txd_next <= tx_data(1);
+                       when 3 =>
+                               txd_next <= tx_data(2);
+                       when 4 =>
+                               txd_next <= tx_data(3);
+                       when 5 =>
+                               txd_next <= tx_data(4);
+                       when 6 =>
+                               txd_next <= tx_data(5);
+                       when 7 =>
+                               txd_next <= tx_data(6);
+                       when 8 =>
+                               txd_next <= tx_data(7);
+                       when 9 =>
+                               txd_next <= '0';
+                       when 10 =>
+                               txd_next <= '1';
+                       when others =>
+                               txd_next <= '1';
+               end case;
+       end process;
+
        tx_done <= '0';
 
 end architecture beh;