- added busout-FIFO for future multi-sourced master capability (VGA-scan, blitter)

Bus-out FIFO improved timing so much and leads to 300 less Slice - FIFOs are great!
Committed on the Free edition of March Hare Software CVSNT Server.
Upgrade to CVS Suite for more features and support:
http://march-hare.com/cvsnt/


git-svn-id: http://moon:8086/svn/vhdl/trunk@666 cc03376c-175c-47c8-b038-4cd826a8556b

lib/VGA_ctrl/src/vga_frontend64.vhd

@@ -142,8 +142,33 @@ architecture Behavioral of vga_frontend64 is
 	signal request_cnt			: natural range 0 to MAX_REQUEST_CNT-1;
 	signal read_cnt				: natural range 0 to MAX_REQUEST_CNT-1;
 	
+	signal STB_O_master			: std_logic;
+	signal ADDR_O_master		: unsigned(31 downto 0);
+	signal pixel_cnt			: natural range 0 to MAX_REQUEST_CNT/2-1;
+	signal front				: unsigned(31 downto 0);
+	signal back					: unsigned(31 downto 0);
+
 	signal odd_pixel			: unsigned(NextExpBaseTwo(tsvga.ts_h.ncyc_scan)-1 downto 0);
 
+	-- Bus FIFO
+	signal bout_fifo_din	: unsigned(104 downto 0);
+	signal bout_fifo_dout	: unsigned(104 downto 0);
+	signal bout_fifo_re		: std_logic;
+	signal bout_fifo_we		: std_logic;
+	signal bout_fifo_full	: std_logic;
+	signal bout_fifo_empty	: std_logic;
+	signal bout_rdy			: std_logic;
+
+	alias bout_fifo_addr_in is bout_fifo_din(31 downto 0);
+	alias bout_fifo_data_in is bout_fifo_din(95 downto 32);
+	alias bout_fifo_sel_in is bout_fifo_din(103 downto 96);
+	alias bout_fifo_we_in is bout_fifo_din(104);
+	
+	alias bout_fifo_addr_out is bout_fifo_dout(31 downto 0);
+	alias bout_fifo_data_out is bout_fifo_dout(95 downto 32);
+	alias bout_fifo_sel_out is bout_fifo_dout(103 downto 96);
+	alias bout_fifo_we_out is bout_fifo_dout(104);
+	
 	type vm_state_t is (init, idle, rdy, bus_request, bus_access, bus_data);
 	signal s, sn : vm_state_t;
 
@@ -242,9 +267,16 @@ inst_linefifo: entity work.fifo_async
 	fifo_color_in		<= MDAT_I;
 	fifo_color_re		<= stat_scan and odd_pixel(0);
 	fifo_color_we		<= ACK_I and read_bus_en;		-- TODO:
+	SRDY_O				<= CYC_I; -- and cg_rdy;
 	MRDY_O				<= not fifo_full;
-	SEL_O				<= (others => '0');
+--	SEL_O				<= (others => '0');
-	WE_O				<= '0';
+--	WE_O				<= '0';
+	STB_O			<= not bout_fifo_empty;
+	ADDR_O			<= bout_fifo_addr_out;
+	MDAT_O			<= bout_fifo_data_out;
+	SEL_O			<= bout_fifo_sel_out;
+	WE_O			<= bout_fifo_we_out;
+
 	
 vga_master_next:
 	process(CLK_I)
@@ -263,7 +295,7 @@ vga_master:
 	begin
 	
 	CYC_O			<= '0';
-	STB_O			<= '0';
+	STB_O_master			<= '0';
 	pixel_cnt_rst	<= '0';
 	request_cnt_rst	<= '0';
 	request_cnt_en	<= '0';
@@ -291,13 +323,13 @@ vga_master:
 		when bus_request =>
 			CYC_O			<= '1';
 			request_cnt_rst	<= '1';
-			if SRDY_I = '1' then
+--			if SRDY_I = '1' then
 				sn	<= bus_access;
-			end if;
+--			end if;
 			
 		when bus_access =>
 			CYC_O			<= '1';
-			STB_O			<= '1';
+			STB_O_master			<= '1';
 			request_cnt_en	<= '1';
 			read_bus_en		<= '1';
 			if fifo_almost_full = '1' then
@@ -324,7 +356,7 @@ request_counter:
 		if rising_edge(CLK_I) then
 			if request_cnt_rst = '1' then
 				request_cnt	<= 0;
-			elsif request_cnt_en = '1' and SRDY_I = '1' then
+			elsif request_cnt_en = '1' and bout_rdy = '1' then
 				if request_cnt /= MAX_REQUEST_CNT-1 then
 					request_cnt <= request_cnt + 1;
 				end if;
@@ -348,30 +380,59 @@ read_counter:
 
 pixel_counter:
 	process(CLK_I)
-	variable pixel_cnt	: natural range 0 to MAX_REQUEST_CNT/2-1;
-	variable front		: unsigned(31 downto 0);
-	variable back		: unsigned(31 downto 0);
 	begin
 		if rising_edge(CLK_I) then
 			bufchg			<= '0';
 			if pixel_cnt_rst = '1' then
-				pixel_cnt	:= 0;
+				pixel_cnt	<= 0;
-				front		:= host_fb_front;
+				front		<= host_fb_front;
-			elsif request_cnt_en = '1' and SRDY_I = '1' then
+			elsif request_cnt_en = '1' and bout_rdy = '1' then
 				if pixel_cnt /= MAX_REQUEST_CNT/2-1 then
-					pixel_cnt 	:= pixel_cnt + 1;
+					pixel_cnt 	<= pixel_cnt + 1;
 				else
-					pixel_cnt	:= 0;
+					pixel_cnt	<= 0;
-					front		:= host_fb_back;
+					front		<= host_fb_back;
 					bufchg		<= '1';
 				end if;	
  			end if;	
 			vga_fb_front	<= front;
  			vga_fb_back		<= back;
- 			ADDR_O			<= front + (to_unsigned(pixel_cnt, 29) & "000");
 		end if;
 	end process;	
 	
+-- Instantiate synchronous FIFO
+inst_bout_fifo: entity work.fifo_sync
+	GENERIC MAP
+	(
+		addr_width	=> 1,
+		data_width	=> 105
+	)
+	PORT MAP
+	(
+		rst			=>	RST_I,
+		clk			=>	CLK_I,
+		we			=>	bout_fifo_we,
+		re			=>	bout_fifo_re,
+		fifo_full	=>	bout_fifo_full,
+		fifo_empty	=>	bout_fifo_empty,
+		fifo_afull	=>	open,
+		fifo_aempty	=>	open,
+		data_w		=>  bout_fifo_din,
+		data_r		=>  bout_fifo_dout
+	);
+	bout_rdy			<= not bout_fifo_full;
+	bout_fifo_re		<= not bout_fifo_empty and SRDY_I;
+	bout_fifo_we		<= STB_O_master and request_cnt_en;
+
+	bout_fifo_data_in	<= (others => '-');
+	bout_fifo_addr_in	<= ADDR_O_master;
+
+	bout_fifo_sel_in	<= (others => '1');
+
+	bout_fifo_we_in		<= '0';
+
+	ADDR_O_master		<= front + (to_unsigned(pixel_cnt, 29) & "000");
+
 inst_char_gen : entity work.char_gen
 	GENERIC MAP
 	(
@@ -408,8 +469,6 @@ inst_char_gen : entity work.char_gen
 	   	csr_pos_y_out	=> cg_csr_pos_y,
 	    char_draw_en	=> cg_draw
     );
-	SRDY_O				<= CYC_I; -- and cg_rdy;
-	MDAT_O				<= (others => '-');
 	scan_rdy			<= stat_hready and stat_vready;
 	cg_en				<= stat_scan;