Memory Map

The following is a memory map that was generated based on the MAME source code (.180).  This information is only as accurate as the MAME driver is.  If you see any errors, please let me know what that error is.
 
The Memory Area is related to where the information is from (CPU, Sound Board, etc..), and it may also reflect what it has in common with other hardware.
Memory Area:defender_bankc000_map
Address RangeLengthFunctionDescription
0x0000-0x000F16Mirror, Write Only, Shared0x03e0, , paletteram
0x0010-0x001F16Mirror, Write0x03e0, defender_video_control_w
0x03FF1Writewilliams_watchdog_reset_w
0x0400-0x04FF256Mirror, RAM Write, Shared0x0300, williams_cmos_w, nvram
0x0800-0x0BFF1024Readwilliams_video_counter_r
0x0C00-0x0C034Mirror, Device Read/Write0x03e0, pia_1, pia6821_device, read, write
0x0001Auto Up / Manual DownActive High
0x0002AdvanceActive High
0x0004Coin 3Active High
0x0008High Score ResetActive High
0x0010Coin 1Active High
0x0020Coin 2Active High
0x0040TiltActive High
0x0080UnknownActive High
0x0C04-0x0C074Mirror, Device Read/Write0x03e0, pia_0, pia6821_device, read, write
0x0001FireActive High
0x0002ThrustActive High
0x0004Smart BombActive High
0x0008HyperspaceActive High
0x0010Start 2Active High
0x0020Start 1Active High
0x0040ReverseActive High
0x0080Joystick DownActive High
0x1000-0x9FFF36864ROM, Regionmaincpu, 0x10000
0xA000-0xFFFF24576Read/Write NOP
Memory Area:defender_map
Address RangeLengthFunctionDescription
0x0000-0xBFFF49152RAM, Sharedvideoram
0xC000-0xCFFF4096Devicebankc000, address_map_bank_device, amap8
0xD000-0xFFFF12288ROM
0xD000-0xDFFF4096Writedefender_bank_select_w
Memory Area:defender_sound_map
Address RangeLengthFunctionDescription
0x0000-0x007F128RAM(/* internal RAM */)
0x0400-0x04034Mirror, Device Read/Write0x8000, pia_2, pia6821_device, read, write
0xB000-0xFFFF20480ROM
Memory Area:sound_map
Address RangeLengthFunctionDescription
0x0000-0x007F128RAM(/* internal RAM */)
0x0080-0x00FF128RAM(/* MC6810 RAM */)
0x0400-0x04034Mirror, Device Read/Write0x8000, pia_2, pia6821_device, read, write
0xB000-0xFFFF20480ROM
Memory Area:williams_map
Address RangeLengthFunctionDescription
0x0000-0x8FFF36864Read Bank, Write Only, Sharedbank1, , videoram
0x9000-0xBFFF12288RAM
0xC000-0xC00F16Mirror, Write Only, Shared0x03f0, , paletteram
0xC804-0xC8074Mirror, Device Read/Write0x00f0, pia_0, pia6821_device, read, write
0x0001FireActive High
0x0002ThrustActive High
0x0004Smart BombActive High
0x0008HyperspaceActive High
0x0010Start 2Active High
0x0020Start 1Active High
0x0040ReverseActive High
0x0080Joystick DownActive High
0xC80C-0xC80F4Mirror, Device Read/Write0x00f0, pia_1, pia6821_device, read, write
0x0001Auto Up / Manual DownActive High
0x0002AdvanceActive High
0x0004Coin 3Active High
0x0008High Score ResetActive High
0x0010Coin 1Active High
0x0020Coin 2Active High
0x0040TiltActive High
0x0080UnknownActive High
0xC900-0xC9FF256Writewilliams_vram_select_w
0xCA00-0xCA078Mirror, Write0x00f8, williams_blitter_w
0xCB00-0xCBFF256Readwilliams_video_counter_r
0xCBFF1Writewilliams_watchdog_reset_w
0xCC00-0xCFFF1024RAM Write, Sharedwilliams_cmos_w, nvram
0xD000-0xFFFF12288ROM
 

ROM Map for this game

 
This is the ROM map for the game.  This should tell you what address the ROM is at, how big it is, what it's used for.   
Memory Area:maincpu
Address RangeLengthLabel/LocationDescription
0xD000-0xD7FF2048"defend.1"CRC(c3e52d7e)
0xD800-0xDFFF2048"defend.4"CRC(9a72348b)
0xE000-0xEFFF4096"defend.2"CRC(89b75984)
0xF000-0xFFFF4096"defend.3"CRC(94f51e9b)
0x10000-0x107FF2048"defend.9"CRC(6870e8a5)
0x10800-0x10FFF2048"defend.12"CRC(f1f88938)
0x11000-0x117FF2048"defend.8"CRC(b649e306)
0x11800-0x11FFF2048"defend.11"CRC(9deaf6d9)
0x12000-0x127FF2048"defend.7"CRC(339e092e)
0x12800-0x12FFF2048"defend.10"CRC(a543b167)
0x16000-0x167FF2048"defend.6"CRC(65f4efd1)
Memory Area:proms
Address RangeLengthLabel/LocationDescription
0x0000-0x01FF512"decoder.2"CRC(8dd98da5)
0x0200-0x03FF512"decoder.3"CRC(c3f45f70)
Memory Area:soundcpu
Address RangeLengthLabel/LocationDescription
0xF800-0xFFFF2048"defend.snd"CRC(fefd5b48)
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