3 files changed, 49 insertions, 21 deletions

diff --git a/basys3/basys3.srcs/io.xdc b/basys3/basys3.srcs/io.xdc
index 419e4cd..218d2f1 100644
--- a/basys3/basys3.srcs/io.xdc
+++ b/basys3/basys3.srcs/io.xdc
@@ -82,3 +82,5 @@ set_property PACKAGE_PIN V19 [get_ports {DBG_LEDS_OUT[3]}]
 set_property PACKAGE_PIN U19 [get_ports {DBG_LEDS_OUT[2]}]
 set_property PACKAGE_PIN E19 [get_ports {DBG_LEDS_OUT[1]}]
 set_property PACKAGE_PIN U16 [get_ports {DBG_LEDS_OUT[0]}]
+
+set_property PULLDOWN true [get_ports SPI_RESET]
diff --git a/basys3/basys3.srcs/spi.vhd b/basys3/basys3.srcs/spi.vhd
index d0e918e..6ca2828 100644
--- a/basys3/basys3.srcs/spi.vhd
+++ b/basys3/basys3.srcs/spi.vhd
@@ -5,20 +5,21 @@ use ieee.std_logic_unsigned.all;
 use work.ppu_consts.all;
 
 entity spi is port (
-	SYSCLK : in std_logic; -- clock basys3 100MHz
+	SYSCLK : in std_logic; -- system clock (100MHz)
 	RESET : in std_logic; -- async reset
 	DCK : in std_logic; -- data clock (spi format)
 	DI : in std_logic; -- data in (spi format)
-	DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '1'); --	data out (parallel)
+	SR : in std_logic; -- sync reset (spi reset)
+	DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '1'); --data out (parallel)
 	WEN : out std_logic := '0'); -- write enable (triggers during each word to propagate previous word)
 end spi;
 
 architecture Behavioral of spi is
-	signal clkFF0,clkFF1,clkFF2,clkFF3 : std_logic := '0'; -- signal for metastability synchronizer of clk SPI
-	signal dataFF0,dataFF1,dataFF2,dataFF3 : std_logic := '0'; -- signal for metastability synchronizer of data SPI
+	signal clkFF0,clkFF1,clkFF2,clkFF3 : std_logic := '0'; -- metastability
+	signal dataFF0,dataFF1,dataFF2 : std_logic := '0'; -- metastability
+	signal srFF0,srFF1,srFF2 : std_logic := '0'; -- metastability
 
 	constant COUNTER_RESET_VALUE : integer := PPU_RAM_BUS_ADDR_WIDTH + PPU_RAM_BUS_DATA_WIDTH - 1;
-	signal DBG_I : integer range 0 to COUNTER_RESET_VALUE := COUNTER_RESET_VALUE; -- counter for data position
 begin
 	process (SYSCLK)
 		variable i : integer range 0 to COUNTER_RESET_VALUE := COUNTER_RESET_VALUE; -- counter for data position
@@ -27,36 +28,60 @@ begin
 		if RESET = '1' then
 			data_r := (others => '1');
 			i := COUNTER_RESET_VALUE;
-			DBG_I <= i;
 			DO <= (others => '1');
 			WEN <= '0';
+			clkFF0 <= '0';
+			clkFF1 <= '0';
+			clkFF2 <= '0';
+			clkFF3 <= '0';
+			dataFF0 <= '0';
+			dataFF1 <= '0';
+			dataFF2 <= '0';
+			srFF0 <= '0';
+			srFF1 <= '0';
+			srFF2 <= '0';
 		elsif rising_edge(SYSCLK) then
-			-- flip flop for clk SPI to synchronise a
 			clkFF0 <= DCK;
 			clkFF1 <= clkFF0;
 			clkFF2 <= clkFF1;
 			clkFF3 <= clkFF2;
-			-- flip flop for data SPI to synchronise
 			dataFF0 <= DI;
 			dataFF1 <= dataFF0;
 			dataFF2 <= dataFF1;
-			dataFF3 <= dataFF2;
+			srFF0 <= SR;
+			srFF1 <= srFF0;
+			srFF2 <= srFF1;
 
-			if (clkFF3 = '0' and clkFF2 = '1') then -- check for rising edge of clk SPI
-				data_r(i) := dataFF3; -- load new data into temporary register
+			if (clkFF3 = '0' and clkFF2 = '1') then
+				data_r(i) := dataFF2;
 
 				if i = 0 then
-					i := COUNTER_RESET_VALUE; -- reset bit index
-					DO <= data_r; -- flush temporary register to data outpu
+					i := COUNTER_RESET_VALUE;
+					DO <= data_r;
 				else
-					i := i - 1; -- decrement bit index
+					i := i - 1;
 				end if;
 
 				-- propagate previous command to ppu during second byte of current command
 				if i = 23 then WEN <= '1'; end if;
 				if i = 15 then WEN <= '0'; end if;
 			end if;
-		DBG_I <= i;
+			if srFF2 = '1' then
+				data_r := (others => '1');
+				i := COUNTER_RESET_VALUE;
+				DO <= (others => '1');
+				WEN <= '0';
+				clkFF0 <= '0';
+				clkFF1 <= '0';
+				clkFF2 <= '0';
+				clkFF3 <= '0';
+				dataFF0 <= '0';
+				dataFF1 <= '0';
+				dataFF2 <= '0';
+				srFF0 <= '0';
+				srFF1 <= '0';
+				srFF2 <= '0';
+			end if;
 		end if;
 	end process;
 end Behavioral;
diff --git a/basys3/basys3.srcs/top.vhd b/basys3/basys3.srcs/top.vhd
index 1c58b60..e69c622 100644
--- a/basys3/basys3.srcs/top.vhd
+++ b/basys3/basys3.srcs/top.vhd
@@ -28,25 +28,26 @@ architecture Behavioral of top is
 		VBLANK : out std_logic); -- vblank for synchronization
 	end component;
 	component spi port (
-		SYSCLK : in std_logic; -- clock basys3 100MHz
+		SYSCLK : in std_logic; -- system clock (100MHz)
 		RESET : in std_logic; -- async reset
 		DCK : in std_logic; -- data clock (spi format)
 		DI : in std_logic; -- data in (spi format)
-		DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '0'); --	data out (parallel)
-		WEN : out std_logic); -- write enable (triggers during each word to propagate previous word)
+		SR : in std_logic; -- sync reset (spi reset)
+		DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '1'); --data out (parallel)
+		WEN : out std_logic := '0'); -- write enable (triggers during each word to propagate previous word)
 	end component;
 
-	signal SPI_RST, PPU_WEN : std_logic;
+	signal PPU_WEN : std_logic;
 	signal SPI_DATA : std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0);
 	alias SPI_DATA_ADDR is SPI_DATA(31 downto 16);
 	alias SPI_DATA_DATA is SPI_DATA(15 downto 0);
 begin
-	SPI_RST <= RESET or SPI_RESET;
 	serial_peripheral_interface: component spi port map(
 		SYSCLK => SYSCLK,
-		RESET => SPI_RST,
+		RESET => RESET,
 		DCK => SPI_CLK,
 		DI => SPI_MOSI,
+		SR => SPI_RESET,
 		DO => SPI_DATA,
 		WEN => PPU_WEN);