diff --git a/Source/QuartusProject/Max10_SD/atari_rom.vhd b/Source/QuartusProject/Max10_SD/atari_rom.vhd
index 13a0c7f..e7fe240 100644
--- a/Source/QuartusProject/Max10_SD/atari_rom.vhd
+++ b/Source/QuartusProject/Max10_SD/atari_rom.vhd
@@ -87,6 +87,7 @@ ARCHITECTURE structure OF atari_rom IS
 	constant CART_TYPE_TURBOSOFT : integer := 36;
 	constant CART_TYPE_ATRAX_128K : integer := 37;
 	constant CART_TYPE_4K : integer := 38;
+	constant CART_TYPE_DCART : integer := 39;
 	constant CART_TYPE_XEX : integer := 254;
 	constant CART_TYPE_NONE : integer := 255;
 
@@ -125,6 +126,9 @@ ARCHITECTURE structure OF atari_rom IS
 	-- SIC d500 byte
 	signal sic_d500_byte : std_logic_vector(7 downto 0);
 	signal sic_read_d500 : boolean := false;
+
+	-- DCART read
+	signal dcart_read_d500 : boolean := false;
 	
 	-- XEX access
 	signal file_offset: std_logic_vector(15 downto 0);
@@ -207,7 +211,7 @@ BEGIN
 	CART_RD5 <= high_bank_enabled;
 	CART_RD4 <= low_bank_enabled;
 	
-	CART_DATA <= data_out when ((CART_S5 = '0' and high_bank_enabled = '1') or (CART_S4 = '0' and low_bank_enabled = '1') or (CART_CTL = '0' and (sic_read_d500 or xex_read_d500))) 
+	CART_DATA <= data_out when ((CART_S5 = '0' and high_bank_enabled = '1') or (CART_S4 = '0' and low_bank_enabled = '1') or (CART_CTL = '0' and (sic_read_d500 or xex_read_d500 or dcart_read_d500))) 
 					else "ZZZZZZZZ";
 	
 	sram_cart_bus_enabled <= '0' when cart_type = CART_TYPE_BOOT else '1';
@@ -227,6 +231,9 @@ BEGIN
 			-- SIC D500-D51F read ?
 			sic_read_d500 <= (cart_type = CART_TYPE_SIC and CART_CTL = '0'
 									and CART_RW = '1' and CART_ADDR(7 downto 5) = "000");
+			-- DCART D500-D5FF read?
+			dcart_read_d500 <= (cart_type = CART_TYPE_DCART and CART_CTL = '0' and CART_RW = '1');
+
 			-- XEX D500-D5FF read ?
 			xex_read_d500 <= (cart_type = CART_TYPE_XEX and CART_CTL = '0' and CART_RW = '1');
 		end if;
@@ -404,6 +411,10 @@ BEGIN
 									bank_out <= "00" & CART_DATA(4 downto 0);
 									sic_d500_byte <= CART_DATA;
 								end if;
+							-- DCART bankswitching
+							when CART_TYPE_DCART => 
+								high_bank_enabled <= not cart_addr_reg(7);
+								bank_out <= '0' & cart_addr_reg(5 downto 0);
 							-- xex loader support - D500,D501 are lo-byte hi-byte of file offset (in 256 byte chunks)
 							when CART_TYPE_XEX =>
 								if (cart_addr_reg(7 downto 0) = x"00") then
@@ -450,7 +461,7 @@ BEGIN
 	-- When we get a new address from the cartridge port, set up the RAM address bus
 	-- to get the correct data
 	process (cart_addr_reg, cart_s4_reg, cart_s5_reg, cart_ctl_reg,
-				cart_type, bank_out, bounty_bob_bank8, bounty_bob_bank9, oss_bank)
+				cart_type, bank_out, bounty_bob_bank8, bounty_bob_bank9, oss_bank,dcart_read_d500)
 	begin
 		fpga_address_in <= (others => '0');
 		sram_address_in <= (others => '0');
@@ -467,7 +478,7 @@ BEGIN
 
 		elsif (cart_type /= CART_TYPE_NONE) then
 		
-			if (cart_s5_reg = '0' or cart_s4_reg = '0') then
+			if (cart_s5_reg = '0' or cart_s4_reg = '0' or dcart_read_d500) then
 				sram_ce <= '1';
 			end if;
 			
@@ -541,6 +552,11 @@ BEGIN
 					end if;
 				when CART_TYPE_4k =>
 					sram_address_in <= "00000000" & cart_addr_reg(11 downto 0); -- 0xB000 access
+				when CART_TYPE_DCART =>
+					if dcart_read_d500 then
+						-- Map to what is B5xx
+						sram_address_in <= bank_out & "10101" & cart_addr_reg(7 downto 0);
+					end if;
 				when others => null;
 			end case;
 			
diff --git a/Source/QuartusProject/Max10_SD/software/sdcard/ultimate.c b/Source/QuartusProject/Max10_SD/software/sdcard/ultimate.c
index d277142..8aabc5b 100644
--- a/Source/QuartusProject/Max10_SD/software/sdcard/ultimate.c
+++ b/Source/QuartusProject/Max10_SD/software/sdcard/ultimate.c
@@ -69,6 +69,7 @@ static int ledVal = 0x1E;
 #define CART_TYPE_TURBOSOFT 		36	// 64k,128k
 #define CART_TYPE_ATRAX_128K		37	// 128k
 #define CART_TYPE_4_K				38  // 4k
+#define CART_TYPE_DCART				39  // 4k
 #define CART_TYPE_XEX				254
 #define CART_TYPE_NONE				255
 
@@ -331,6 +332,7 @@ int load_cart(char *filename)
 					cart_type = CART_TYPE_4_K;
 					memset(dst32, 255, 4096);
 				}
+				else if (car_type == 112) cart_type = CART_TYPE_DCART;
 				else { cart_type = -2; break; }	// unsupported car type
 				bytesToCopy -= 16;
 				src32 += 4;