Address decode masks

Decode masks aren't verified !

Decode masks are used to know which register will be mapped to a given address, they can be seen as a sort of mirroring range notation.

A "1" bit means that the corresponding address bit is involved in decoding, a "0" means it's ignored.

For example, REG_P1CNT's base is $300000 and its mask is $FE0001:

BASE 00110000 00000000 00000000
MASK 11111110 00000000 00000001
     0011000x xxxxxxxx xxxxxxx0

This means that it's also accessible at $300002, $300004, $300006... up to $31FFFE. The highest address is BASE OR (NOT MASK).

Mirror guesser

Register descriptions

I/O registers

REG_P1CNT

Read

Write

Joypad port 1 inputs (active low)

Bit	7	6	5	4	3	2	1	0
Def	D	C	B	A	Right	Left	Down	Up

?

Address: $300000
Decode mask: $FE0001
Handled by: NEO-C1

REG_DIPSW

Read

Write

Hardware DIPs (active low)

Bit	7	6	5	4	3	2	1	0
Def	Freeze game	Freeplay	Enable Multiplayer	Multiplayer ID code		0:Normal controller 1:Mahjong keyboard	0:1 coin chute 1:2 coin chutes	Settings mode

Kick watchdog

Address: $300001
Decode mask: $FE0081 (not sure for write)
Handled by: NEO-F0 (read), NEO-B1 (write)

REG_SYSTYPE

Read

Write

Bit	7	6	5	4	3	2	1	0
Def	Test button	Type 0: 2 slots 1: 4 or 6 slots	?

?

Reads the unused DSW2 on MV4 boards. Used for system ID on other boards.

Address: $300081
Decode mask: $FE0081
Handled by: NEO-F0

REG_SOUND

Read	Write
Read Z80 reply code	Send command to Z80

Address: $320000
Decode mask: $FE0001
Handled by: NEO-C1

REG_STATUS_A

Read

Write

Switch inputs are active low

Bit	7	6	5	4	3	2	1	0
Def	RTC data bit	RTC time pulse	0:4-SLOT 1:6-SLOT	Coin-in 4	Coin-in 3	Service button	Coin-in 2	Coin-in 1

?

Address: $320001
Decode mask: $FE0001
Handled by: NEO-F0

REG_P2CNT

Read

Write

Joypad port 2 inputs (active low)

Bit	7	6	5	4	3	2	1	0
Def	D	C	B	A	Right	Left	Down	Up

?

Address: $340000
Decode mask: $FE0001
Handled by: NEO-C1

REG_STATUS_B

Read

Write

Aux inputs (lower bits active low)

Bit	7	6	5	4	3	2	1	0
Def	0:AES 1:MVS	Memory card write protected if 1	Memory card inserted if 00		Select P2	Start P2	Select P1	Start P1

?

Address: $380000
Decode mask: $FE0001
Handled by: NEO-C1

REG_POUTPUT

Read

Write

?

Joypad ports outputs

Bit	7	6	5	4	3	2	1	0
Def	?		P2 outputs			P1 outputs

Address: $380001
Decode mask: $FE0071
Handled by: NEO-D0

REG_CRDBANK

Read

Write

?

Bit	7	6	5	4	3	2	1	0
Def						Memory card bank selection

Address: $380011
Decode mask: $FE0071
Handled by: NEO-D0

REG_SLOT

Read

Write

?

Bit	7	6	5	4	3	2	1	0
Def	?					Slot #

(Mirror of REG_POUTPUT on the AES)

Address: $380021
Decode mask: $FE00F1
Handled by: NEO-F0

REG_LEDLATCHES

Read

Write

?

Bit	7	6	5	4	3	2	1	0
Def	?		Latch LED2 data	Latch LED1 data	Latch marquee data	?

LED data is latched on 1 to 0 transition.

Address: $380031
Decode mask: $FE00F1
Handled by: NEO-F0

REG_LEDDATA

Read	Write
?	8-bit data for credits displays and the marquee. See MV-LED.

Address: $380041
Decode mask: $FE00F1
Handled by: NEO-F0

REG_RTCCTRL

Read

Write

?

MAME upd4990a_control_16_w

Bit	7	6	5	4	3	2	1	0
Def						RTC Strobe	RTC Clock	RTC DIN

Address: $380051
Decode mask: $FE00F1
Handled by: NEO-F0

REG_RESETCC1

Read	Write
?	Any, coin counter 1 floats

Address: $380061
Decode mask: $FE00F1
Handled by: NEO-I0

REG_RESETCC2

Read	Write
?	Any, coin counter 2 floats

Address: $380063
Decode mask: $FE00F1
Handled by: NEO-I0

REG_RESETCL1

Read	Write
?	Any, coin lockout 1 floats

Address: $380065
Decode mask: $FE00F1
Handled by: NEO-I0

REG_RESETCL2

Read	Write
?	Any, coin lockout 2 floats

Address: $380067
Decode mask: $FE00F1
Handled by: NEO-I0

REG_SETCC1

Read	Write
?	Any, coin counter 1 sinks current

Address: $3800E1
Decode mask: $FE00F1
Handled by: NEO-I0

REG_SETCC2

Read	Write
?	Any, coin counter 2 sinks current

Address: $3800E3
Decode mask: $FE00F1
Handled by: NEO-I0

REG_SETCL1

Read	Write
?	Any, coin lockout 1 sinks current

Address: $3800E5
Decode mask: $FE00F1
Handled by: NEO-I0

REG_SETCL2

Read	Write
?	Any, coin lockout 2 sinks current

Address: $3800E7
Decode mask: $FE00F1
Handled by: NEO-I0

System registers

Data written doesn't matter. Odd byte writes only. Decode mask: $FE0001.

Registers go in pairs, bit 4 of the address is actually the data bit.

Handled by a 74HC259 addressable latch on cart systems.

Address	Name	Write
$3A0001	REG_NOSHADOW	Normal video output
$3A0011	REG_SHADOW	Darken video output
$3A0003	REG_SWPBIOS	BIOS vector table
$3A0013	REG_SWPROM	Use the cart's vector table
$3A0005	REG_CRDUNLOCK1	Enable writes to memory card (unused in CD systems)
$3A0015	REG_CRDLOCK1	Disable writes to memory card (unused in CD systems)
$3A0007	REG_CRDLOCK2	Disable writes to memory card (unused in CD systems)
$3A0017	REG_CRDUNLOCK2	Enable writes to memory card (unused in CD systems)
$3A0009	REG_CRDREGSEL	Enable "Register select" for memory card
$3A0019	REG_CRDNORMAL	Disable "Register select" for memory card
$3A000B	REG_BRDFIX	Use the embedded SFIX ROM and SM1 ROM
$3A001B	REG_CRTFIX	Use the cart's S ROM and M1 ROM
$3A000D	REG_SRAMLOCK	Write-protects backup RAM (MVS)
$3A001D	REG_SRAMUNLOCK	Unprotects backup RAM (MVS)
$3A000F	REG_PALBANK1	Use palette bank 1
$3A001F	REG_PALBANK0	Use palette bank 0

Video registers

Handled by the LSPC. Byte writes are only effective on even addresses and they store the same data in both bytes. Odd addresses aren't mapped ? Decode mask: $FE0001.

Address

Name

Read

Write

$3C0000

REG_VRAMADDR

Read from VRAM (address doesn't change)

Sets VRAM address

$3C0002

REG_VRAMRW

Read from VRAM (address doesn't change)

Write to VRAM (modulo is applied after)

$3C0004

REG_VRAMMOD

Reads VRAM address modulo

Sets VRAM address modulo

$3C0006

REG_LSPCMODE

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Def	Raster line counter. See Display timing									0			1:50Hz 0:60Hz (LSPC2 only)	Auto animation counter

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Def	Auto animation speed (in frames)								Timer interrupt mode			Timer interrupt enable	Disable auto animation	Unused

Reset value: ????????00000---

$3C0008

REG_TIMERHIGH

Like REG_VRAMADDR.

16 highest bits of the timer reload value.

$3C000A

REG_TIMERLOW

Like REG_VRAMRW.

16 lowest bits of the timer reload value.

$3C000C

REG_IRQACK

Like REG_VRAMMOD.

Interrupt acknowledge.

Bit	7	6	5	4	3	2	1	0
Def	Unused					Ack VBlank IRQ	Ack timer IRQ	Ack IRQ3

$3C000E

REG_TIMERSTOP

Like REG_LSPCMODE.

Bit 0=1: Stops timer counter during first and last 16 lines (32 total) when in PAL mode.

NeoGeo CD registers

NEO-MGA / LC8953 / LC98000 ?

CD drive

Address

Name

Size

Read

Write

Handled by

$FF0161

REG_CDDINPUT

Byte

Bit	7	6	5	4	3	2	1	0
Def	-			CDCK input	4-bit bus from the CD drive

?

NEO-MGA

$FF0163

REG_CDDOUTPUT

Byte

?

Bit	7	6	5	4	3	2	1	0
Def	-				4-bit bus to the CD drive

NEO-MGA

$FF0165

REG_CDDCTRL

Byte

?

Bit	7	6	5	4	3	2	1	0
Def	-				Must be 0		Signal selection 0:4-bit bus direction 1:HOCK output	State Dir:0:Out 1:In HOCK:0:Low 1:High

NEO-MGA

$FF0167

REG_CDDSTAT

Byte

CD drive status lines.

Bit	7	6	5	4	3	2	1	0
Def	-			MUTE	SBSO	SCOR	WFCK	EXCK

Bit	7	6	5	4	3	2	1	0
Def	-							EXCK

NEO-MGA

Video

Address	Name	Size	Read	Write	Handled by
$FF0111	REG_DISBLSPR	Byte	?	1=Disable 0=Enable sprites	NEO-GRC/NEO-OFC
$FF0115	REG_DISBLFIX	Byte	?	1=Disable 0=Enable fix layer
$FF0119	REG_ENVIDEO	Byte	?	1=Enable 0=Disable video output.

Memory

Address	Name	Size	Read	Write	Handled by
$FF01A1	REG_SPRBANK	Byte	?	Upload zone 1MiB SPR DRAM bank selection (2 LSBs).	?
$FF01A3	REG_PCMBANK	Byte	?	Upload zone 512KiB PCM DRAM bank selection (1 LSB).	?
$FF01A7	REG_???BANK	Byte	?	$A00000 zone bank number. What is this ?	?
$FF0121	REG_UPMAPSPR	Byte	?	NeoSetSpriteSlot(1); Set upload zone to SPR DRAM	?
$FF0123	REG_UPMAPPCM			Set upload zone to PCM DRAM
$FF0127	REG_UPMAPZ80			Set upload zone to Z80 DRAM
$FF0129	REG_UPMAPFIX			Set upload zone to FIX DRAM
$FF0141	REG_UPUNMAPSPR			Unset SPR DRAM to upload zone
$FF0143	REG_UPUNMAPPCM			Unset PCM DRAM to upload zone
$FF0147	REG_UPUNMAPZ80			Unset Z80 DRAM to upload zone
$FF0149	REG_UPUNMAPFIX			Unset FIX DRAM to upload zone

DMA

Address	Name	Size	Read	Write	Handled by
$FF0061	?	Byte	?	Bit 6: Execute DMA microcode	LC8953
$FF0064~$FF0067	REG_DMA_ADDR1	Longword	?	Sets DMA source address.
$FF0068~$FF006B	REG_DMA_ADDR2	Longword	?	Sets DMA destination address.
$FF006C~$FF006F	REG_DMA_VALUE	Longword	?	Sets DMA value for filling.
$FF0070~$FF0073	REG_DMA_COUNT	Longword	?	Sets DMA length.
$FF007E	REG_DMA_MODE	Word	?	Sets DMA mode.
$FF007E~$FF008E	?	Words	?	Microcode (16x 9-bit opcodes)

Neo CD specific

Address

Name

Size

Read

Write

Handled by

$FF0002

?

Word

?

Enables Vector 22 interrupts. NeoRaine calls load_files.

LC8953

$FF0004

?

Word

?

CDM3-2 BIOS writes 0,1,3,7

$FF0006

?

Word

?

CDM3-2 BIOS writes 0x71FF, CDZ writes 0x71FF

$FF0008

?

Word

?

CDM3-2 BIOS writes 0x0000, CDZ writes 0x0000

$FF000A

?

Word

?

CDM3-2 BIOS writes 0x7E40, CDZ writes 0x7E00

$FF000C

?

Word

?

Read and stored on vector 23 interrupt.

$FF000F

?

Byte

?

Interrupt acknowledge.

Bit	7	6	5	4	3	2	1	0
Def	?		Vector 21	Vector 22	Vector 23	?

$FF0010/11

?

Byte

?

CDM3-2 BIOS writes $FE

$FF0017

?

Byte

CD mode, maybe CDDA mute ? Bit 0: 0=Audio 1=Data.

?

$FF0101

?

Byte

LC8951 register address (4 LSB)

LC89515

$FF0103

?

Byte

LC8951 register value

$FF0105

REG_TRANSAREA

Byte

?

Set active transfer area

0:Sprites
1:ADPCM
4:Z80
5:Fix

?

$FF0108

?

Word

?

CDM3-2 BIOS writes $5555

?

$FF010C

?

Word

?

CDM3-2 BIOS writes $5555 and reads

?

$FF011C

REG_CDCONFIG

Word

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Def	1		CD Mech 0:TOP/CDZ 1:FRONT	Lid Status (Opposite on CDZ)	Configuration jumpers				?

?

NEO-CDD board

$FF016D

Byte

?

MapVectorTable(!(byteValue == 0xFF));

NEO-MGA

$FF016F

REG_UPLOAD_EN

Byte

?

Enable/disable writes to the upload zone ($E00000)

$FF0181

REG_CDIRQ_EN

Byte

?

Bit 0: Enable CD drive interrupt

$FF0183

REG_Z80RST

Byte

?

Active-low Z80 RESET ($0/$FF)

CDDA

Address	Name	Size	Read	Write	Handled by
$FF0188	REG_CDDALEFTL	Word	See Reading CDDA sound levels	No effect	NEO-MGA
$FF018A	REG_CDDARIGHTL	Word	See Reading CDDA sound levels	No effect	NEO-MGA
$FF01FC	?	Word	?	CDDA control ?	?
$FF01FE	?	Word	?	CD music/data switch ?	?

Memory mapped registers

Contents

Address decode masks

Mirror guesser

Register descriptions

I/O registers

REG_P1CNT

REG_DIPSW

REG_SYSTYPE

REG_SOUND

REG_STATUS_A

REG_P2CNT

REG_STATUS_B

REG_POUTPUT

REG_CRDBANK

REG_SLOT

REG_LEDLATCHES

REG_LEDDATA

REG_RTCCTRL

REG_RESETCC1

REG_RESETCC2

REG_RESETCL1

REG_RESETCL2

REG_SETCC1

REG_SETCC2

REG_SETCL1

REG_SETCL2

System registers

Video registers

NeoGeo CD registers

CD drive

Video

Memory

DMA

Neo CD specific

CDDA

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