Add quirk for Ys (Japan) to fix graphics bug (#132)

SMS.sv

@@ -498,6 +498,25 @@ sdramclk_ddr
 reg  rom_wr = 0;
 wire sd_wrack;
 reg  [23:0] romwr_a;
+reg  ysj_quirk = 0;
+
+always @(posedge clk_sys) begin
+	reg [31:0] cart_id;
+	reg old_download;
+	old_download <= cart_download;
+
+	if(~old_download && cart_download) {ysj_quirk} <= 0;
+
+	if(ioctl_wr & cart_download) begin
+		if(ioctl_addr == 'h7ffc) cart_id[31:24] <= ioctl_dout[7:0];
+		if(ioctl_addr == 'h7ffd) cart_id[23:16] <= ioctl_dout[7:0];
+		if(ioctl_addr == 'h7ffe) cart_id[15:08] <= ioctl_dout[7:0];
+		if(ioctl_addr == 'h7fff) cart_id[07:00] <= ioctl_dout[7:0];
+		if(ioctl_addr == 'h8000) begin
+			if(cart_id == 32'h13_70_01_4F) ysj_quirk <= 1; // Ys (Japan) Graphics Fix, forces VDP Version 1
+		end
+	end
+end
 
 always @(posedge clk_sys) begin
 	reg old_download, old_reset;
@@ -673,6 +692,7 @@ system #(63) system
 	.smode_M1(smode_M1),
 	.smode_M2(smode_M2),
 	.smode_M3(smode_M3),
+	.ysj_quirk(ysj_quirk),
 	.pal(pal),
 	.region(status[10]),
 	.mapper_lock(status[15] && ~systeme),
@@ -777,7 +797,7 @@ always @(posedge clk_sys) begin
 		joya_th <=  swap ? 1'b1 : joyser_th;
 		joyb_th <=  swap ? joyser_th : 1'b1;
 
-		USER_OUT <= {swap ? joyb_tr_out : joya_tr_out, 1'b1, swap ? joyb_th_out : joya_th_out, 4'b1111, };
+		USER_OUT <= {swap ? joyb_tr_out : joya_tr_out, 1'b1, swap ? joyb_th_out : joya_th_out, 4'b1111 };
 
 	end else begin
 		joya <= ~joy[jcnt];
@@ -861,7 +881,7 @@ video video
 	.border(border),
 	.mask_column(mask_column),
 	.cut_mask(status[29]),
-   .smode_M1(smode_M1),
+	.smode_M1(smode_M1),
 	.smode_M3(smode_M3),
 	.x(x),
 	.y(y),

rtl/system.vhd

@@ -82,6 +82,7 @@ entity system is
 		smode_M1:		out STD_LOGIC;
 		smode_M2:		out STD_LOGIC;
 		smode_M3:		out STD_LOGIC;
+		ysj_quirk:		in	STD_LOGIC;
 		pal:				in STD_LOGIC;
 		region:			in	STD_LOGIC;
 		mapper_lock:	in STD_LOGIC;
@@ -349,6 +350,7 @@ begin
 		smode_M1  => smode_M1,
 		smode_M2  => smode_M2,
 		smode_M3  => smode_M3,
+		ysj_quirk	=> ysj_quirk,
 		mask_column => mask_column,
 		black_column => black_column,
 		reset_n  => RESET_n
@@ -385,6 +387,7 @@ begin
 --		smode_M1  => smode2_M1,
 --		smode_M2  => smode2_M2,
 --		smode_M3  => smode2_M3,
+		ysj_quirk	=> ysj_quirk,
 --		mask_column => mask2_column,
 		black_column => black_column,
 		reset_n  => RESET_n

rtl/vdp.vhd

@@ -35,6 +35,7 @@ entity vdp is
 		smode_M2: 		out STD_LOGIC;
 		smode_M3: 		out STD_LOGIC;
 		smode_M4: 		out STD_LOGIC;
+		ysj_quirk:		in  STD_LOGIC;
 		reset_n:       in  STD_LOGIC);
 end vdp;
 
@@ -144,6 +145,7 @@ begin
 		smode_M1			=> xmode_M1,
 		smode_M3			=> xmode_M3,
 		smode_M4			=> xmode_M4,
+		ysj_quirk			=> ysj_quirk,
 						
 		display_on		=> display_on,
 		mask_column0	=> mask_column0,

rtl/vdp_background.vhd

@@ -16,6 +16,7 @@ port (
 	smode_M1:			in  std_logic;
 	smode_M3:			in  std_logic;
 	smode_M4:			in  std_logic;
+	ysj_quirk:			in  std_logic;
 	y:						in  std_logic_vector(7 downto 0);
 	screen_y:			in  std_logic_vector(8 downto 0);
 
@@ -85,16 +86,13 @@ begin
 						char_address(12 downto 5) := table_address(13 downto 12) & ("011100" + y(7 downto 3));
 					else
 						char_address(12 downto 10)	:= table_address(13 downto 11);
-
-					   -- To enable version 1 of the VDP found on the SMS version 1, and you'd want to do that
-						-- to play only one game : Japanese version of "Ys", you can re-enable the comment in the next code line.
-						--
-						-- Since there seems to be no difference between the Japanese version of Ys and the US one, there is no reasonable need
-						-- to implement a way to select the code below manually or automatically.
-
-						char_address(9) := -- table_address(10) and 
-													y(7) ;
-						char_address(8 downto 5)	:= y(6 downto 3);						
+						if ysj_quirk = '1' then -- Enable VDP version 1 for Ys (Japan)
+							char_address(9) := table_address(10) and y(7);
+							char_address(8 downto 5) := y(6 downto 3);
+						else
+							char_address(9) := y(7);
+							char_address(8 downto 5) := y(6 downto 3);
+						end if;
 					end if;
 					char_address(4 downto 0)	:= x(7 downto 3) + 1;
 					data_address					:= tile_index & tile_y;

rtl/vdp_main.vhd

@@ -31,6 +31,7 @@ entity vdp_main is
 		smode_M1:			in  std_logic;
 		smode_M3:			in  std_logic;
 		smode_M4:			in  std_logic;
+		ysj_quirk:			in  std_logic;
 		overscan:			in  std_logic_vector (3 downto 0);
 
 		bg_address:			in  std_logic_vector (3 downto 0);
@@ -104,6 +105,7 @@ begin
 		smode_M1			=> smode_M1,
 		smode_M3			=> smode_M3,
 		smode_M4			=> smode_M4,
+		ysj_quirk			=> ysj_quirk,
 		
 		priority			=> bg_priority);