Added cursor support and teletext pass-through to video ULA. Fixed a couple of cursor bugs in the CRTC.

2 files changed, 56 insertions, 5 deletions

diff --git a/mc6845.vhd b/mc6845.vhd
index 30cf333..90c1108 100644
--- a/mc6845.vhd
+++ b/mc6845.vhd
@@ -395,7 +395,11 @@ begin
 			cursor_i <= '0';

 			cursor_line := '0';

 		elsif rising_edge(CLOCK) and CLKEN = '1' then

-			if ma_i = r14_cursor_h & r15_cursor_l then

+			if h_display = '1' and v_display = '1' and ma_i = r14_cursor_h & r15_cursor_l then

+				if line_counter = 0 then

+					-- Suppress wrap around if last line is > max scan line

+					cursor_line := '0';

+				end if;

 				if line_counter = r10_cursor_start then

 					-- First cursor scanline

 					cursor_line := '1';

diff --git a/vidproc.vhd b/vidproc.vhd
index 485cd15..0825081 100644
--- a/vidproc.vhd
+++ b/vidproc.vhd
@@ -65,6 +65,13 @@ signal delayed_disen	:	std_logic;
 signal clken_pixel		:	std_logic;

 signal clken_counter	:	unsigned(3 downto 0);

 

+-- Cursor generation - can span up to 32 pixels

+-- Segments 0 and 1 are 8 pixels wide

+-- Segment 2 is 16 pixels wide

+signal cursor_invert	:	std_logic;

+signal cursor_active	:	std_logic;

+signal cursor_counter	:	unsigned(4 downto 0);

+

 begin

 	-- Synchronous register access, enabled on every clock

 	process(CLOCK,nRESET)

@@ -145,6 +152,38 @@ begin
 		end if;

 	end process;

 	

+	-- Cursor generation

+	cursor_invert <= cursor_active and

+		((r0_cursor0 and not (cursor_counter(4) or cursor_counter(3))) or

+		(r0_cursor1 and cursor_counter(3) and not cursor_counter(4)) or

+		(r0_cursor2 and cursor_counter(4)));

+	process(CLOCK,nRESET)

+	begin

+		if nRESET = '0' then

+			cursor_active <= '0';

+			cursor_counter <= (others => '0');

+		elsif rising_edge(CLOCK) and CLKEN = '1' then

+			if CURSOR = '1' or cursor_active = '1' then

+				-- Latch cursor

+				cursor_active <= '1';

+		

+				-- Reset on counter wrap

+				if cursor_counter = "11111" then

+					cursor_active <= '0';

+				end if;

+				

+				-- Increment counter

+				if cursor_active = '0' then

+					-- Reset

+					cursor_counter <= (others => '0');

+				else

+					-- Increment

+					cursor_counter <= cursor_counter + 1;

+				end if;

+			end if;

+		end if;

+	end process;

+	

 	-- Pixel generation

 	-- The new shift register contents are loaded during

 	-- cycle 0 (and 8) but will not be read here until the next cycle.

@@ -179,10 +218,18 @@ begin
 			blue_val := (dot_val(3) and r0_flash) xor not dot_val(2);

 		

 			-- To output

-			-- FIXME: Cursor and INVERT option, teletext

-			R <= red_val and delayed_disen;

-			G <= green_val and delayed_disen;

-			B <= blue_val and delayed_disen;

+			-- FIXME: INVERT option

+			if r0_teletext = '0' then

+				-- Cursor can extend outside the bounds of the screen, so

+				-- it is not affected by DISEN

+				R <= (red_val and delayed_disen) xor cursor_invert;

+				G <= (green_val and delayed_disen) xor cursor_invert;

+				B <= (blue_val and delayed_disen) xor cursor_invert;

+			else

+				R <= R_IN;

+				G <= G_IN;

+				B <= B_IN;

+			end if;

 			

 			-- Display enable signal delayed by one clock

 			delayed_disen <= DISEN;