bugnotes.txt

i fixed some real nasty bugs

	set_incr_vars: process (int_pixel_local_x, int_char_x, int_pixel_local_y,
		int_char_y, int_mem_addr, hstate, vstate) is
	begin
		if hstate = HActiveVideo and vstate = VActiveVideo then
			if int_pixel_local_x = CHAR_WIDTH - 1 then
				incr_char_x <= true;
			else
				incr_char_x <= false;
			end if;

			if incr_char_x and int_char_x = TXT_DISP_WIDTH - 1 then
				incr_pixel_local_y <= true;
			else
				incr_pixel_local_y <= false;
			end if;

			if incr_pixel_local_y and int_pixel_local_y = CHAR_HEIGHT - 1 then
				incr_char_y <= true;
			else
				incr_char_y <= false;
			end if;

			if incr_char_x and int_mem_addr = MEM_BYTES - 1 then
				incr_mem_bank <= true;
			else
				incr_mem_bank <= false;
			end if;
		else
			incr_char_x <= false;
			incr_pixel_local_y <= false;
			incr_char_y <= false;
			incr_mem_bank <= false;
		end if;
	end process;
	
	see the pre-anding expression? those weren't there, before which
	they would just fire off for however long that the previous statement
	didnt update. would have never seen this had i not pushed it through 
	the simulator.
	i guess testing really is a neccesary evil.
	
	another nasty bug in the char address unit regarding bank settings.
	
	evil alert:
	these 2 snippets are not equivalent despite appearances:
	
	if rising_edge(pixel_clk) then
		if have_new_char(pipeline(2)) then
			scratchpad.glyph <= get_gb(char);
		end if;
	end if;
	
	if rising_edge(pixel_clk) and have_new_char(pipeline(2)) then
		scratchpad.glyph <= get_gb(char);
	end if;
	
	the reason is, ofcourse, is the above 'and' statement is not logical, but
	of 'std_logic' type, and thus causes gated clock DRC warnings to occur.
	
	The correct version would be
	
	if rising_edge(pixel_clk) and have_new_char(pipeline(2)) = '1' then
		scratchpad.glyph <= get_gb(char);
	end if;
	
	**NEVERMIND**, the above are both boolean.
	in that case, i really dont know. the only explanation is that whether or
	not you embed or not the cond actually matters.
	
	found missing pixel on "y":
		constant bitmap_Yu: glyph_bitmap := (
		"10000010",
		"10000010",
		"01000100",
		"00111010",
		"00010000",
		"00010000",
		"00010000",
		"00000000"
	);
	
	another missing pixel on '$':
		constant bitmap_DOLLAR: glyph_bitmap := (
		"00010000",
		"01111100",
		"10000000",
		"01111000",
		"00000010",
		"01111100",
		"00010000",
		"00000000"
	);
	
	I also fixed the caret symbol from looking too much like a vertical
	curly brace.
	I think that the less-than/larger-than symbols could do with a similar
	treatment, but i'll leave them be for now.