69 lines
1.7 KiB
OCaml
69 lines
1.7 KiB
OCaml
open Printf
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(** http://bgb.bircd.org/pandocs.htm#cpuregistersandflags
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http://gameboy.mongenel.com/dmg/lesson1.html *)
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type registers = {
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mutable a : char; (* accumulator *)
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mutable f : char; (* flags *)
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mutable b : char;
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mutable c : char;
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mutable d : char;
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mutable e : char;
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mutable h : char;
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mutable l : char;
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mutable sp : int; (* stack pointer *)
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mutable pc : int; (* program counter *)
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}
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(* type flags = {
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z : bool; (* zero *)
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n : bool; (* substraction *)
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h : bool; (* half-carry *)
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cy : bool; (* carry *)
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} *)
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type t = {
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reg : registers;
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mutable cycles : int;
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}
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(** http://bgb.bircd.org/pandocs.htm#powerupsequence *)
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let init_registers =
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{
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a = '\x00';
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f = '\x00';
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b = '\x00';
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c = '\x00';
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d = '\x00';
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e = '\x00';
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h = '\x00';
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l = '\x00';
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sp = 0xFFFE;
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pc = 0x0100;
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}
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let init_cpu =
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{ reg = init_registers; cycles = 0 }
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let inc_pc cpu count =
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cpu.reg.pc <- cpu.reg.pc + count
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let inc_cycles cpu count =
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cpu.cycles <- cpu.cycles + count
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let read_2B b addr =
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let low = Bytes.get b addr in
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let high = Bytes.get b (addr + 1) in
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(int_of_char high) * 256 + (int_of_char low)
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(** http://imrannazar.com/GameBoy-Z80-Opcode-Map *)
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let run cpu (cartridge: Cartridge.t) =
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(* Hexa.print_slice cartridge.full_rom cpu.reg.pc (cpu.reg.pc + 7) ~width:16; *)
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match Bytes.get cartridge.full_rom cpu.reg.pc with
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| '\x00' -> printf " nop\n"; inc_pc cpu 1; inc_cycles cpu 4
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| '\xC3' -> let addr = read_2B cartridge.full_rom (cpu.reg.pc + 1) in
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printf " jp 0x%02x\n" addr; cpu.reg.pc <- addr; inc_cycles cpu 16
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| _ as x -> eprintf "OpCode %02X\n" (int_of_char x); failwith "Unimplemented opcode."
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