Add pattern generator for demoing the scrolling behaviour

main.vhd

@@ -35,6 +35,9 @@ architecture syn of main is
     signal clk_vga: std_logic;
 
     signal reset: std_logic;
+
+    signal write_enable: std_logic;
+    signal write_data: std_logic_vector(7 downto 0);
 begin
 
     reset <= switch_center;
@@ -48,10 +51,8 @@ begin
     terminal: entity work.terminal port map (
         clk => clk_vga,
         reset => reset,
-
+        write_enable => write_enable,
-        write_enable => '0',
+        write_data => write_data,
-        write_data => x"00",
-
         dvi_d => dvi_d,
         dvi_clk_p => dvi_clk_p,
         dvi_clk_n => dvi_clk_n,
@@ -63,6 +64,42 @@ begin
         i2c_sda => i2c_sda
     );
 
+    -- write an example text pattern to test the terminal
+    process(clk_vga, reset)
+        variable delay: integer range 0 to 300_000;
+        variable line: integer range 0 to 90;
+        variable max: integer range 0 to 90;
+    begin
+        if reset = '1' then
+            delay := 0;
+            line := 0;
+            max := 0;
+        elsif rising_edge(clk_vga) then
+            write_enable <= '0';
+
+            if delay = 300_000 then
+                write_enable <= '1';
+                write_data <= "0" & std_logic_vector(to_unsigned(33 + line, 7));
+
+                if line = max then
+                    write_data <= x"0a";
+                    line := 0;
+                    if max = 90 then
+                        max := 0;
+                    else
+                        max := max + 1;
+                    end if;
+                else
+                    line := line + 1;
+                end if;
+
+                delay := 0;
+            else
+                delay := delay + 1;
+            end if;
+        end if;
+    end process;
+
     keyboard_i: entity work.keyboard generic map (
         input_clk => clk_vga_f
     ) port map (