Add basic support for MBC.

src/cartridge.ml

@@ -9,7 +9,7 @@ type t = {
   full_rom : bytes;
   nintendo_logo : bytes;
   title : string;
-(*  mem_type : memory_bank_controller; *)
+  mem_type : memory_bank_controller;
   rom_size : int;
   ram_size : int;
 (*  header_checksum : bytes;
@@ -24,6 +24,16 @@ let check_nintendo_logo cartridge =
   \xBB\xBB\x67\x63\x6E\x0E\xEC\xCC\xDD\xDC\x99\x9F\xBB\xB9\x33\x3E" in
   (Bytes.compare cartridge.nintendo_logo reference) == 0
 
+let get_cartridge_type = function
+  | 0x00 -> ROM_ONLY
+  | 0x01 -> MBC1
+  | x -> Printf.printf "%02X\n" x; failwith "Invalid cartridge type."
+
+let mem_type_name = function
+  | ROM_ONLY -> "ROM_ONLY"
+  | MBC1 -> "MBC1"
+
+
 (** ROM size is expressed in KB *)
 let get_ROM_size = function
   | 0x00 -> 32 (* no ROM banking *)
@@ -69,6 +79,10 @@ let read_cartridge file =
       let title_b = Bytes.sub full_rom title_offset title_size in
       let title = Bytes.to_string title_b in
 
+      (* Cartridge type - memory bank *)
+      let mem_type_code = Bytes.get full_rom 0x0147 |> int_of_char in
+      let mem_type = get_cartridge_type mem_type_code in
+
       (* ROM size *)
       let rom_size_code = Bytes.get full_rom 0x0148 |> int_of_char in
       let rom_size = get_ROM_size rom_size_code in
@@ -77,9 +91,17 @@ let read_cartridge file =
       let ram_size_code = Bytes.get full_rom 0x0149 |> int_of_char in
       let ram_size = get_RAM_size ram_size_code in
 
-      Some { full_rom; nintendo_logo; title; rom_size; ram_size }
+      Some { full_rom; nintendo_logo; title; mem_type; rom_size; ram_size }
 
   with
   | Sys_error msg
   | Invalid_argument msg (* This is triggered by Bytes.sub *)
   | Failure msg -> prerr_endline msg; None
+
+
+let print_info cartridge =
+  let open Printf in
+  printf "Title: %s\n" cartridge.title;
+  printf "Mem. type: %s\n" (cartridge.mem_type |> mem_type_name);
+  printf "ROM size: %iKB\n" cartridge.rom_size;
+  printf "RAM size: %iKB\n" cartridge.ram_size

src/cpu.ml

@@ -99,7 +99,11 @@ let run cpu (cartridge: Cartridge.t) =
               printf "  JP \t0x%04X\n" addr;
               cpu.reg.pc <- addr; inc_cycles cpu 16
 
-  | '\xE0' -> printf "  LDH \t(0x%02X), A\n" (int_of_char n);
+  | '\xE0' -> printf "  LDH \t(0xFF%02X), A\n" (int_of_char n);
+              (* fixme *)
+              inc_pc cpu 2; inc_cycles cpu 12
+
+  | '\xF0' -> printf "  LDH \tA, (0xFF%02X)\n" (int_of_char n);
               (* fixme *)
               inc_pc cpu 2; inc_cycles cpu 12
 

src/oboy.ml

@@ -12,9 +12,7 @@ let power_up cartridge =
   then print_endline "Invalid ROM."
   else
     print_endline "Valid ROM.";
-    printf "Title: %s\n" cartridge.title;
+    Cartridge.print_info cartridge;
-    printf "ROM size: %iKB\n" cartridge.rom_size;
-    printf "RAM size: %iKB\n" cartridge.ram_size;
 
     let cpu = Cpu.init_cpu in
     run cpu cartridge