Merge branch 'dev' into ppu-interface

1 files changed, 34 insertions, 0 deletions

diff --git a/basys3/basys3.srcs/er_ram_mod.vhd b/basys3/basys3.srcs/er_ram_mod.vhd
new file mode 100644
index 0000000..ae680b1
--- /dev/null
+++ b/basys3/basys3.srcs/er_ram_mod.vhd
@@ -0,0 +1,34 @@
+library ieee;
+library work;
+use ieee.std_logic_1164.all;
+
+entity er_ram_mod is -- exposed register RAM module (single register)
+	generic(
+		W : natural := 1; -- module data width
+		ADDR_W : natural := 1; -- address width
+		ADDR_M : std_logic_vector(ADDR_W-1 downto 0) := (others => '0')); -- address match
+	port(
+		CLK : in std_logic; -- clock
+		RST : in std_logic; -- async memory clear
+		WEN : in std_logic; -- write enable
+		ADDR : in std_logic_vector(ADDR_W-1 downto 0); -- RAM address line
+		DATA : in std_logic_vector(W-1 downto 0); -- RAM input data line
+		REG : out std_logic_vector(W-1 downto 0)); -- direct register output lines
+end er_ram_mod;
+
+architecture Behavioral of er_ram_mod is
+	signal DATA_REG : std_logic_vector(W-1 downto 0);
+begin
+	REG <= DATA_REG;
+
+	process(CLK, RST)
+	begin
+		if RST = '1' then
+			DATA_REG <= (others => '0');
+		elsif rising_edge(CLK) then
+			if WEN = '1' and ADDR = ADDR_M then
+				DATA_REG <= DATA;
+			end if;
+		end if;
+	end process;
+end Behavioral;