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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.
Sky Alert (Metro, 1992)
Memory Area:metro_sound_io_map
Address RangeLengthFunctionDescription
0x00001Writemetro_sound_rombank_w
0x00001Read/Writemetro_porta_r, metro_porta_w
0x00001Writemetro_portb_w
Memory Area:metro_sound_map
Address RangeLengthFunctionDescription
0x0000-0x3FFF16384ROM(/* External ROM */)
0x4000-0x7FFF16384ROM Bankbank1 (/* External ROM (Banked) */)
0x8000-0x87FF2048RAM(/* External RAM */)
0xFF00-0xFFFF256RAM(/* Internal RAM */)
Memory Area:skyalert_map
Address RangeLengthFunctionDescription
0x0000-0x3FFFF262144ROM(// ROM)
0x400000-0x4000012Read/Writemetro_soundstatus_r,metro_soundstatus_w (// From / To Sound CPU)
0x400002-0x4000032Read NOP, Writemetro_coin_lockout_1word_w (// Coin Lockout)
0x400004-0x4000052Read PortIN0 (// Inputs)
0x400006-0x4000072Read PortIN1 (//)
0x400008-0x4000092Read PortIN2 (//)
0x40000A-0x40000B2Read PortDSW0 (//)
0x40000C-0x40000D2Read PortDSW1 (//)
0x0003DifficultyActive High
0x0002EasyActive High
0x0003NormalActive High
0x0001HardActive High
0x0000HardestActive High
0x000cLivesActive High
0x00081Active High
0x00042Active High
0x000c3Active High
0x00004Active High
0x0030Bonus_LifeActive High
0x0030100K, every 400KActive High
0x0020200K, every 400KActive High
0x0010200KActive High
0x0000NoneActive High
0x0040Allow_ContinueActive High
0x0000NoActive High
0x0040YesActive High
0x0080Demo_SoundsActive High
0x0000OffActive High
0x0080OnActive High
0x40000E-0x40000F2Read PortIN3 (//)
0xffffUnknownActive Low
0x800000-0x81FFFF131072RAM Write, Sharedmetro_vram_0_w, vram_0 (// Layer 0)
0x820000-0x83FFFF131072RAM Write, Sharedmetro_vram_1_w, vram_1 (// Layer 1)
0x840000-0x85FFFF131072RAM Write, Sharedmetro_vram_2_w, vram_2 (// Layer 2)
0x860000-0x86FFFF65536Readmetro_bankedrom_r (// Banked ROM)
0x870000-0x871FFF8192RAM(// ???)
0x872000-0x873FFF8192RAM Device Write, Sharedpalette, palette_device, write, palette (// Palette)
0x874000-0x874FFF4096RAM, Sharedspriteram (// Sprites)
0x878000-0x8787FF2048RAM, Sharedtiletable (// Tiles Set)
0x878800-0x87881320Write Only, Sharedvideoregs (// Video Registers)
0x878840-0x87884D14Write, Sharedmetro_blitter_w, blitter_regs (// Tiles Blitter)
0x878860-0x87886B12Write, Sharedmetro_window_w, window (// Tilemap Window)
0x878870-0x87887B12Write Only, Sharedscroll (// Scroll)
0x878880-0x8788812Write NOP(// ? CRT)
0x878890-0x8788912Write NOP(// ? CRT)
0x8788A2-0x8788A32Read/Writemetro_irq_cause_r,metro_irq_cause_w (// IRQ Cause / IRQ Acknowledge)
0x8788A4-0x8788A52Write Only, Sharedirq_enable (// IRQ Enable)
0x8788A8-0x8788A92Writemetro_soundlatch_w (// To Sound CPU)
0x8788AA-0x8788AB2Write Only, Sharedrombank (// Rom Bank)
0x8788AC-0x8788AD2Write Only, Sharedscreenctrl (// Screen Control)
0xC00000-0xC0FFFF65536RAM, Mirror0x0f0000 (// RAM (mirrored))
 

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:audiocpu
Address RangeLengthLabel/LocationDescription
0x0000-0x3FFF16384sa_b_12.binCRC(f358175d) (Fluke: 13D9)
Memory Area:oki
Address RangeLengthLabel/LocationDescription
0x0000-0x1FFFF131072sa_a_11.binCRC(04842a60) (Fluke: 9413)
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