68k memory map

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In Cartridge systems

To do: More details in the $300000 range, especially mirroring. See MAME's source and address decoding signals.

Start End Size DEF Name Wait cycles Description
$000000 $0FFFFF 1MiB 0 or 1 (4/5 clks) depending on Sig.pngROMWAIT. Vector table, first fixed bank of the Chipicon.png 68k program ROM (Chipicon.png P ROM)
$100000 $10F2FF 64KiB WORKRAM 0 (4 clks) User RAM
$10F300 $10FFFF System ROM-reserved RAM
$110000 $1FFFFF 0 (4 clks) Work RAM mirror
$200000 $2FFFFF 1MiB 0 to 3 (4/7 clks) depending on Sig.pngPWAIT. Second bank of the 68k program ROM (also used for bankswitching and access to special chips)
$300000 $3FFFFF 0 (4 clks) I/O. See Memory mapped registers and GPU.
$400000 $401FFF 8KiB PALETTES 0 (4 clks) Banked palette RAM
$402000 $7FFFFF 0 (4 clks) Palette RAM mirror
$800000 $BFFFFF 8 MiB max MEMCARD 2 (6 clks) Memory card
$C00000 $C1FFFF 128KiB SYSTEMROM 0 (4 clks) System ROM
$C20000 $CFFFFF 0 (4 clks) System ROM mirror
$D00000 $D0FFFF 64KiB 0 (4 clks) Backup RAM (MVS only)
$D10000 $DFFFFF 0 (4 clks) Backup RAM mirror

In CD systems

Start End Size DEF Name Description
$000000 $0FFFFF 2MiB Vector table, 68k program (PRG files), 68k RAM
$100000 $10F2FF 64KiB
Shared with the 68k code DRAM.
WORKRAM User RAM
$10F300 $10FFFF System ROM-reserved RAM
$110000 $1FFFFF 68k program ?
$300000 $39FFFF Input ports (See Memory mapped registers)
$3A0000 $3BFFFF Ouput ports (See Memory mapped registers)
$3C0000 $3FFFFF GPU ports (See Memory mapped registers)
$400000 $401FFF 8KiB PALETTES Banked palette RAM
$800000 $803FFF 8 KiB MEMCARD Virtual memory card (onboard battery-backed RAM)

(8bit, even bytes are always $FF)

$C00000 $C7FFFF 512KiB BIOSROM System ROM
$D00000 $DFFFFF  ?
$E00000 $EFFFFF 1MiB UPLOAD Upload zone
$FF0000 $FF01FF ? CD and DMA specific I/O registers

For Neo Print boards

Infos from [MAME's source].

Start End Size DEF Name Description
$000000 $07FFFF 512KiB 68k program (P ROM).
$100000 $17FFFF Banked 68k program or I/O (writes done here).
$200000 $20FFFF 64KiB 68k RAM
$300000 $30FFFF 64KiB Backup RAM
$400000 $43FFFF VRAM ?
$500000 $51FFFF 128KiB Palette RAM
$600000 $600001 Z80 I/O
$600002 $600003 RTC I/O
$600004 $60000D I/O registers
$700000 $70001B GPU registers
70001E 70001F Watchdog