X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/8e2bb38447e731bbba10c39cfb995b9b4eccd22c..41341eb3bab6479dc763afbe90c7c31a01d6b60f:/LCDC.v

diff --git a/LCDC.v b/LCDC.v
index f951d3a..cb204d5 100644
--- a/LCDC.v
+++ b/LCDC.v
@@ -21,13 +21,17 @@ module LCDC(
 	output wire lcdclk, lcdvs, lcdhs,
 	output reg [2:0] lcdr, lcdg, output reg [1:0] lcdb);
 	
+	/***** Bus latches *****/
+	reg rdlatch = 0;
+	reg [15:0] addrlatch = 0;
+	
 	/***** Needed prototypes *****/
 	wire [1:0] pixdata;
 	
 	/***** Internal clock that is stable and does not depend on CPU in single/double clock mode *****/
 	reg clk4 = 0;
 	always @(posedge clk)
-		clk4 = ~clk4;
+		clk4 <= ~clk4;
 	
 	/***** LCD control registers *****/
 	reg [7:0] rLCDC = 8'h00;
@@ -88,7 +92,7 @@ module LCDC(
 	assign lcdcirq = (rSTAT[3] & mode00irq) | (rSTAT[4] & mode01irq) | (rSTAT[5] & mode10irq) | (rSTAT[6] & lycirq);
 	assign vblankirq = (posx == 0 && posy == 153);
 	
-	always @(negedge clk4)
+	always @(posedge clk4)
 	begin
 		if (posx == 455) begin
 			posx <= 0;
@@ -146,7 +150,7 @@ module LCDC(
 	wire [10:0] tileaddr = {tileno, vypos[2:0]};
 	reg [7:0] tilehigh, tilelow;
 	wire [1:0] prepal = {tilehigh[7-vxpos[2:0]], tilelow[7-vxpos[2:0]]};
-	assign pixdata = {rBGP[{prepal,1'b1}],rBGP[{prepal,1'b0}]};
+	assign pixdata = 2'b11-{rBGP[{prepal,1'b1}],rBGP[{prepal,1'b0}]};
 	
 	wire decode_tiledata = (addr >= 16'h8000) && (addr <= 16'h97FF);
 	wire decode_bgmap1 = (addr >= 16'h9800) && (addr <= 16'h9BFF);
@@ -155,13 +159,12 @@ module LCDC(
 	wire [11:0] tileaddr_in = vraminuse ? tileaddr : addr[12:1];
 	
 	always @(posedge clk)
+	begin
 		if ((vraminuse && ((posx == 2) || (vxpos[2:0] == 3'b111))) || decode_bgmap1) begin
 			tileno <= bgmap1[bgmapaddr_in];
 			if (wr && decode_bgmap1 && ~vraminuse)
 				bgmap1[bgmapaddr_in] <= data;
 		end
-	
-	always @(posedge clk)
 		if ((vraminuse && ((posx == 3) || (vxpos[2:0] == 3'b000))) || decode_tiledata) begin
 			tilehigh <= tiledatahigh[tileaddr_in];
 			tilelow <= tiledatalow[tileaddr_in];
@@ -170,28 +173,31 @@ module LCDC(
 			if (wr && ~addr[0] && decode_tiledata && ~vraminuse)
 				tiledatalow[tileaddr_in] <= data;
 		end
+	end
   
 	/***** Bus interface *****/
-	assign data = rd ?
-			((addr == `ADDR_LCDC) ? rLCDC :
-			 (addr == `ADDR_STAT) ? {rSTAT[7:3], (rLYC == posy) ? 1'b1 : 1'b0, mode} :
-			 (addr == `ADDR_SCY) ? rSCY :
-			 (addr == `ADDR_SCX) ? rSCX :
-			 (addr == `ADDR_LY) ? posy :
-			 (addr == `ADDR_LYC) ? rLYC :
-			 (addr == `ADDR_BGP) ? rBGP :
-			 (addr == `ADDR_OBP0) ? rOBP0 :
-			 (addr == `ADDR_OBP1) ? rOBP1 :
-			 (addr == `ADDR_WY) ? rWY :
-			 (addr == `ADDR_WX) ? rWX :
-			 (decode_tiledata && addr[0]) ? tilehigh :
-			 (decode_tiledata && ~addr[0]) ? tilelow :
+	assign data = rdlatch ?
+			((addrlatch == `ADDR_LCDC) ? rLCDC :
+			 (addrlatch == `ADDR_STAT) ? {rSTAT[7:3], (rLYC == posy) ? 1'b1 : 1'b0, mode} :
+			 (addrlatch == `ADDR_SCY) ? rSCY :
+			 (addrlatch == `ADDR_SCX) ? rSCX :
+			 (addrlatch == `ADDR_LY) ? posy :
+			 (addrlatch == `ADDR_LYC) ? rLYC :
+			 (addrlatch == `ADDR_BGP) ? rBGP :
+			 (addrlatch == `ADDR_OBP0) ? rOBP0 :
+			 (addrlatch == `ADDR_OBP1) ? rOBP1 :
+			 (addrlatch == `ADDR_WY) ? rWY :
+			 (addrlatch == `ADDR_WX) ? rWX :
+			 (decode_tiledata && addrlatch[0]) ? tilehigh :
+			 (decode_tiledata && ~addrlatch[0]) ? tilelow :
 			 (decode_bgmap1) ? tileno :
 			 8'bzzzzzzzz) :
 		8'bzzzzzzzz;
   
 	always @(posedge clk)
 	begin
+		rdlatch <= rd;
+		addrlatch <= addr;
 		if (wr)
 			case (addr)
 			`ADDR_LCDC:	rLCDC <= data;