1 files changed, 51 insertions, 0 deletions
diff --git a/basys3/basys3.srcs/ppu_addr_dec.vhdl b/basys3/basys3.srcs/ppu_addr_dec.vhdl
new file mode 100644
index 0000000..28c22fc
--- /dev/null
+++ b/basys3/basys3.srcs/ppu_addr_dec.vhdl
@@ -0,0 +1,51 @@
+library ieee;
+library work;
+use ieee.std_logic_1164.all;
+--use ieee.numeric_std.all;
+use work.ppu_consts.all;
+
+entity ppu_addr_dec is port(
+	EN: in std_logic; -- EXT *ADDR enable (switch *AO to ADDR instead of *AI)
+	WEN: in std_logic; -- EXT write enable
+	TMM_WEN,
+	BAM_WEN,
+	FAM_WEN,
+	PAL_WEN,
+	AUX_WEN: out std_logic; -- write enable MUX
+	ADDR: in std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH-1 downto 0); -- address in
+	TMM_AI: in std_logic_vector(PPU_TMM_ADDR_WIDTH-1 downto 0);
+	BAM_AI: in std_logic_vector(PPU_BAM_ADDR_WIDTH-1 downto 0);
+	FAM_AI: in std_logic_vector(PPU_FAM_ADDR_WIDTH-1 downto 0);
+	PAL_AI: in std_logic_vector(PPU_PAL_ADDR_WIDTH-1 downto 0);
+	AUX_AI: in std_logic_vector(PPU_AUX_ADDR_WIDTH-1 downto 0);
+	TMM_AO: out std_logic_vector(PPU_TMM_ADDR_WIDTH-1 downto 0);
+	BAM_AO: out std_logic_vector(PPU_BAM_ADDR_WIDTH-1 downto 0);
+	FAM_AO: out std_logic_vector(PPU_FAM_ADDR_WIDTH-1 downto 0);
+	PAL_AO: out std_logic_vector(PPU_PAL_ADDR_WIDTH-1 downto 0);
+	AUX_AO: out std_logic_vector(PPU_AUX_ADDR_WIDTH-1 downto 0));
+end ppu_addr_dec;
+
+architecture Behavioral of ppu_addr_dec is
+	signal TMM_RANGE, BAM_RANGE, FAM_RANGE, PAL_RANGE, AUX_RANGE: std_logic := '0'; -- ADDR in range of memory area
+begin
+	-- address MUX
+	TMM_AO <= ADDR(PPU_TMM_ADDR_WIDTH-1 downto 0) when EN = '1' else TMM_AI;
+	BAM_AO <= ADDR(PPU_BAM_ADDR_WIDTH-1 downto 0) when EN = '1' else BAM_AI;
+	FAM_AO <= ADDR(PPU_FAM_ADDR_WIDTH-1 downto 0) when EN = '1' else FAM_AI;
+	PAL_AO <= ADDR(PPU_PAL_ADDR_WIDTH-1 downto 0) when EN = '1' else PAL_AI;
+	AUX_AO <= ADDR(PPU_AUX_ADDR_WIDTH-1 downto 0) when EN = '1' else AUX_AI;
+
+	-- WEN MUX
+	TMM_WEN <= TMM_RANGE and WEN;
+	BAM_WEN <= BAM_RANGE and WEN;
+	FAM_WEN <= FAM_RANGE and WEN;
+	PAL_WEN <= PAL_RANGE and WEN;
+	AUX_WEN <= AUX_RANGE and WEN;
+
+	-- address ranges
+	TMM_RANGE <= '1' when not (ADDR(15) = '1' and ADDR(14) = '1') else '0';
+	BAM_RANGE <= '1' when (ADDR(15) = '1' and ADDR(14) = '1') and (ADDR(11) = '0') else '0';
+	FAM_RANGE <= '1' when (ADDR(15) = '1' and ADDR(14) = '1') and (ADDR(11) = '1' and ADDR(10) = '0') else '0';
+	PAL_RANGE <= '1' when (ADDR(15) = '1' and ADDR(14) = '1') and (ADDR(11) = '1' and ADDR(10) = '1' and ADDR(9) = '0') else '0';
+	AUX_RANGE <= '1' when (ADDR(15) = '1' and ADDR(14) = '1') and (ADDR(11) = '1' and ADDR(10) = '1' and ADDR(9) = '1') else '0';
+end Behavioral;