history/display: backspace logic

[hwmod.git] / src / history.vhd

diff --git a/src/history.vhd b/src/history.vhd
index 08b035904f5fae303825cae44c3214d7ed2fa9c4..b1a1b0193f6f3aa9412d4c29381f1808c614b852 100644 (file)
--- a/src/history.vhd
+++ b/src/history.vhd
@@ -17,6 +17,7 @@ entity history is
                -- Display
                d_new_eingabe : out std_logic;
                d_new_result : out std_logic;
+               d_new_bs : out std_logic;
                d_zeile : in hzeile;
                d_spalte : in hspalte;
                d_get : in std_logic;
@@ -35,10 +36,12 @@ architecture beh of history is
        type HISTORY_STATE is (SIDLE, S_S_INIT, S_S_WRITE, S_S_BS, S_S_DONE, S_S_FIN,
                S_D_INIT, S_D_WRITE);
        signal state_int, state_next : HISTORY_STATE;
+       signal was_bs_int, was_bs_next : std_logic;
        signal s_done_int, s_done_next : std_logic;
        signal s_cnt_int, s_cnt_next : hspalte;
        signal d_new_eingabe_int, d_new_eingabe_next : std_logic;
        signal d_new_result_int, d_new_result_next : std_logic;
+       signal d_new_bs_int, d_new_bs_next: std_logic;
        signal d_done_int, d_done_next : std_logic;
        signal d_char_int, d_char_next : hbyte;
 
@@ -52,6 +55,7 @@ begin
        s_done <= s_done_int;
        d_new_eingabe <= d_new_eingabe_int;
        d_new_result <= d_new_result_int;
+       d_new_bs <= d_new_bs_int;
        d_done <= d_done_int;
        d_char <= d_char_int;
 
@@ -62,11 +66,13 @@ begin
                if sys_res_n = '0' then
                        -- internal
                        state_int <= SIDLE;
+                       was_bs_int <= '0';
                        -- out
                        s_done_int <= '0';
                        s_cnt_int <= (0 => '1', others => '0');
                        d_new_result_int <= '0';
                        d_new_eingabe_int <= '0';
+                       d_new_bs_int <= '0';
                        d_done_int <= '0';
                        d_char_int <= (others => '0');
 
@@ -78,11 +84,13 @@ begin
                elsif rising_edge(sys_clk) then
                        -- internal
                        state_int <= state_next;
+                       was_bs_int <= was_bs_next;
                        -- out
                        s_done_int <= s_done_next;
                        s_cnt_int <= s_cnt_next;
                        d_new_result_int <= d_new_result_next;
                        d_new_eingabe_int <= d_new_eingabe_next;
+                       d_new_bs_int <= d_new_bs_next;
                        d_done_int <= d_done_next;
                        d_char_int <= d_char_next;
 
@@ -95,9 +103,10 @@ begin
        end process;
 
        -- next state
-       process(state_int, d_get, do_it, s_take, s_backspace)
+       process(state_int, d_get, do_it, s_take, s_backspace, was_bs_int)
        begin
                state_next <= state_int;
+               was_bs_next <= was_bs_int;
 
                case state_int is
                        when SIDLE =>
@@ -115,8 +124,11 @@ begin
                                else
                                        state_next <= S_S_WRITE;
                                end if;
-                       when S_S_WRITE | S_S_BS =>
+                       when S_S_WRITE =>
+                               state_next <= S_S_DONE;
+                       when S_S_BS =>
                                state_next <= S_S_DONE;
+                               was_bs_next <= '1';
                        when S_S_FIN =>
                                if do_it = '0' then
                                        state_next <= SIDLE;
@@ -124,6 +136,7 @@ begin
                        when S_S_DONE =>
                                if s_take = '0' then
                                        state_next <= SIDLE;
+                                       was_bs_next <= '0';
                                end if;
 
                        when S_D_INIT =>
@@ -137,12 +150,15 @@ begin
 
        -- out
        process(state_int, s_cnt_int, d_spalte, data_out, s_char, address_int,
-               data_in_int, d_new_result_int, d_new_eingabe_int)
+               data_in_int, d_new_result_int, d_new_eingabe_int, d_new_bs_int,
+               was_bs_int)
+               variable addr_tmp : std_logic_vector(H_RAM_WIDTH - 1 downto 0);
        begin
                s_done_next <= '0';
                s_cnt_next <= s_cnt_int;
                d_new_result_next <= d_new_result_int;
                d_new_eingabe_next <= d_new_eingabe_int;
+               d_new_bs_next <= '0';
                d_done_next <= '0';
                d_char_next <= (others => '0');
                finished_next <= '0';
@@ -151,30 +167,38 @@ begin
                data_in_next <= data_in_int;
 
                case state_int is
-                       when S_S_INIT =>
-                               null;
                        when SIDLE =>
                                -- TODO: tmp fix
                                d_new_result_next <= '0';
+                       when S_S_INIT =>
+                               null;
                        when S_S_WRITE =>
                                wr_next <= '1';
                                address_next <= s_cnt_int;
                                data_in_next <= s_char;
                                s_cnt_next <= std_logic_vector(unsigned(s_cnt_int) + 1);
                        when S_S_BS =>
+                               -- ab 1 darf nicht mehr dekrementiert werden
+                               if unsigned(s_cnt_int) /= 1 then
+                                       addr_tmp := std_logic_vector(unsigned(s_cnt_int) - 1);
+                                       d_new_bs_next <= '1';
+                               else
+                                       addr_tmp := s_cnt_int;
+                               end if;
+                               s_cnt_next <= addr_tmp;
+               
                                wr_next <= '1';
-                               address_next <= std_logic_vector(unsigned(s_cnt_int) - 1);
+                               address_next <= addr_tmp;
                                data_in_next <= (others => '0');
-                               if unsigned(s_cnt_int) /= 0 then
-                                       s_cnt_next <= std_logic_vector(unsigned(s_cnt_int) - 1);
-                               end if;
                        when S_S_FIN =>
                                finished_next <= '1';
                                s_cnt_next <= (0 => '1', others => '0');
                                d_new_result_next <= '1';
                        when S_S_DONE =>
                                s_done_next <= '1';
-                               d_new_eingabe_next <= '1';
+                               if was_bs_int = '0' then
+                                       d_new_eingabe_next <= '1';
+                               end if;
 
                        when S_D_INIT =>
                                address_next <= d_spalte;