Z80 Assembly programming for the MSX and MSX2

The MSX and later the MSX2 were an attermpt to create a 'PC' before the PC!... based around the 8-bit processor, an 'industry standard' compatible computer specification was created, and any manufacturer could realease compatible hardware.

With 2 extension slots, the machine was upgradable, and the end user could be confident that their hardware and software would work whatever MSX machine they had!

The last generation MSX - the Turbo-R was hugely powerful, and it's upgradability means the MSX now has the V9990... combining the Turbo-R and the V9990 (V9K) we effectively have what would have been the MSX3 if it had not been cancelled

Because each MSX has different hardware, we can only generalize, but here's the hardware specification you can expect to see!
Specs:

	MSX	MSX2	Turbo-R	V9990
Cpu	3.5mhz Z80	3.5mhz Z80	7mhz R800 (28mhz effective)
Ram	16k	64k	256k / 512k
Vram	16k	128k	128k	512k (9x MSX2 speed)
Resolution	256x192	256x212	256x212	256x212
Colors	16	16	256	256
Sprites	32 sprites 8x8 or 16x16
Sound chip	AY	AY	AY + PCM

The V9990 can be used with the MSX, or MSX2 as well! - not just the Turbo-R

Although the Turbo-R does not use a Z80, the R800 has effectively perfect compatibility, although it's 'only' 7mhz , it uses memory caching, and in optimum circumstances can perform 4x the speed of a 7mhz Z80

ChibiAkumas Tutorials

	Lesson H3 - Hello World on the MSX / MSX2
	Lesson S5 - Easy Sprites on the MSX2
	Lesson P1 - Basic Firmware Text functions
	Lesson P2 - More Text Functions, Improvements... and the Sam Coupe!
	Lesson P5 - Bitmap graphics on the TI-83 and MSX
	Lesson P7 - Keyreading on the MSX, Enterprise and TI-83
	Lesson P10 - Tilemap graphics on the MSX1
	Lesson P11 - Tilemap graphics on the MSX2
	Lesson P15 - Palette definitions on the MSX2 and V9990
	Lesson P18 - Making Sound with the AY-3-8910 on the Amstrad CPC, MSX,ZX Spectrum.... and NeoGeo + Atari ST!!
	Lesson P25 - Bankswitching and hardware detection on the MSX
	Lesson P31 - Hardware Sprites on the Master System / Game Gear and MSX1!
	Lesson P35 - Playing Digital Sound with WAV on the AY-3-8910!
	Lesson P48 - All MSX2 Bitmap Commands - Part 1/2
	Lesson P49 - All MSX2 Bitmap Commands - Part 2/2
	Lesson P50 - Alternative Bitmap modes... HighRes, 256 color, YJK (MSX2+) and Interlaced!
	Lesson P52 - MSX1 mode G2 for 768 onscreen tiles
	Lesson P59 - Hardware scrolling on the MSX 1/2/2+
	Lesson P64 - Mouse reading on the MSX
	Lesson P69 - ChibiSound PRO on the CPC, MSX and Spectrum (128 - AY) [CPC] [MSX] [ZXS]

MSX Documents

9918 - MSX1 VDP
V9938 - MSX2 VDP
V9958 - MSX2+ VDP

Default Memory Map

CBIOS MSX1
With cartridge in Slot 1/A

&0000-&3FFF	Rom Slot 0
&4000-&7FFF	Cart Slot 1
&8000-&BFFF	Ram Slot 3
&C000-&FFFF	Ram Slot 3

Panasonic FS-A1F MSX2
With cartridge in Slot 1/A

&0000-&3FFF	Rom Slot 0
&4000-&7FFF	Cart Slot 1
&8000-&BFFF	Ram Slot 3-0
&C000-&FFFF	Ram Slot 3-0

Panasonic FS-A1F MSX2
In basic

&0000-&3FFF	Rom Slot 0
&4000-&7FFF	Rom Slot 0
&8000-&BFFF	Ram Slot 3-0
&C000-&FFFF	Ram Slot 3-0

MSX Banks, Slots and Subslots... Oh my!:
The MSX memory layout is far more advanced and powerful than other 8 bits... unfortunately that tends to just mean that it's more annoying!

Take a look at an MSX! You'll see it has 1 or usually 2 cartridge slots... right?... well actually there are two extra slots! 0 and 3 are 'internal' slots used by the system itself... so we have slots 0-3... simple right... actually no!

A 'Slot' can (but is not always) be split into 4 subslots... also numbered 0 to 3
EVERYTHING is in a slot, so RAM and ROM are in a slot somewhere... but unfortunately they aren't in the same place on all machines!... Slot 1 and 2 are always the cartridge slots, but the RAM could be in slot 3, or in slot 0-2 (slot 0 subslot 2)

It's all quite annoying!

The MSX memory map is split into 4 16K chunks, and each bank can be 'pointed' to one of the 3 slots... If the slot is expanded, each of these banks can be set to a different subslot... so bank 0 can point to 0-0 (slot 0 subslot 0), and bank 1 can point to 0-2 (slot 0 subslot 2)... while banks 2 and 3 could point to slot 3!

It needs to be understood that each slot has 4 banks for a full 64k - so when bank 0 and 1 points to slot 3-0... they are different 16k chunks... also in this case it is not possible to swap them round... Bank 0 (&0000-&3FFF) of the Z80 memory cannot point to bank 1 (&4000-&7FFF) of the Slot

So suppose we have the following set up:

	Subslots
Slot 0	0-0	0-1	0-2	0-3
*Slot 1*	1	Unexpanded slot
*Slot 2*	2-0	2-1	2-2	2-3
Slot 3	3-0	3-1	3-2	3-3

ROM

RAM

Cartridge

Empty

Z80 Banks
The Z80 address range is split into 4 banks of 16k
We may see a systems setup at boot in the following... .Remember Slot 3-0 will have 4 different memory banks, but they can only be mapped into the matching positions of the Z80 address range.

*** We can only map a Z80 bank to the MATCHING slot bank!

Slot Selection Register
Which Slot the Z80 will see in each bank is defined by the slot selection register at port &A8... it's 8 bits define all 4 banks slot number... each 2 bits define the slot number for an area of the address range

Port &A8 Bits	7	6	5	4	3	2	1	0
Bank number	3 (&C000-&FFFF)		2 (&8000-&BFFF)		1 (&4000-&7FFF)		0 (&0000-&3FFF)

Sub-Slot Selection
Not all slots are expanded.... but it's easy to tell if they are, on boot addresses &FCC1-&FCC4 will be configured to record if slots 0-3 are expanded... the top bit (bit 7) will be 1 if they are

If a slot IS expanded... there will be a memory mapped register at memory address &FFFF

the format is the same as the slot selection register

Slot 0 &FFFF Bits	7	6	5	4	3	2	1	0
Subslot number	3 (&C000-&FFFF)		2 (&8000-&BFFF)		1 (&4000-&7FFF)		0 (&0000-&3FFF)

Memory Mappers
As mentioned, we can only map a bank of ram in a slot to the matching bank in the Z80 range... wouldn't it be nice if we could map a bank of ram to ANY bank of the Z80 range?

Well actually we can!... in theory!
A slot CAN have something called a 'Memory Mapper'... what's this? well it allows exactly what I just mentioned... any one of the 16k banks in the slot can be mapped to the that slots position... we still need to map in the slot (and subslot if required) but that slot can expose any bank of memory... this also allows us to address more than 64k... we can have up to 512k!

We select a slots memory mapping using 4 ports... note we can only write to these - we cannot rely on reading from them

Port	Z80 Address range	Default value
&FC	&0000-&3FFF	3
&FD	&4000-&7FFF	2
&FE	&8000-&BFFF	1
&FF	&C000-&FFFF	0

A system may have more than one Memory mapper...one internal, and one in an upgrade... but they will all set at the same time with these ports... we will still need to page in the slot-subslot using the usual method to get access to the memory.

So Memory mappers are more flexible, and allow more memory... what's not to like?.... well almost NO MSXes have them... even with the MSX2+, most MSXes do not have them... so unless your game is Turbo-R only, you're not going to be able to use them!

Cartridge Mappers
Cartridges also have 'mappers'... though they work differently - we just WRITE the bank number to a special address in the ROM, and the ROM will switch it's bank for us!

There are various mappers, but we'll look at "Konami with SCC" (Konami5) , it provides 4 rom areas that can be reconfigured - note they do not cover the whole Z80 range - as the bottom bank is assumed to be ROM, and the top bank is assumed to be RAM

Area	Z80 Address Range	Write Address to change bank	Default Value
1	&4000-&5FFF	&5000	0
2	&6000-&7FFF	&7000	1
3	&8000-&9FFF	&9000	2
4	&A000-&BFFF	&B000	3

Minimum MSX configurations
So what can we expect from our MSXes memory wise, well here's what you need to assume you'll have!

System	MSX1	MSX2	MSX2+	Turbo-R
Memory	16k	64k	64k	256K
Disk System?	NO	NO (sometimes)	NO (usually - not always)	YES
Mapper?	NO	NO	NO (sometimes)	YES

Soooo.... Effectively on the MSX1 we're pretty much going to have to rely on using Cartrige ROM, and we won't be able to use a Memory Mapper unless we're using the Turbo-R as the minimum requirement.

Joystick Reading

On the MSX the joysticks are connected to the AY data port.
We select an AY register with port &A0, we set one with port &A1, and read one with port &A2

First we need to set the bottom 4 bits of AY register 15 to 1 - this is to enable input of pins 6/7 of the joysick and to select Joystick 0.

Next we select AY register 14 - This will allow us to read in from the joystick.

Finally we read in from port &A2, this gets the actual state of the joystick and it's two fires in the format %--21RLDU

Keyboard matrix

&AA	bit 7	bit 6	bit 5	bit 4	bit 3	bit 2	bit 1	bit 0
row 0	7 &	6 ^	5 %	4 $	3 #	2 @	1 !	0 )
row 1	; :	] }	[ {	\ �	= +	- _	9 (	8 *
row 2	B	A	DEAD	/ ?	. >	, <	` ~	' "
row 3	J	I	H	G	F	E	D	C
row 4	R	Q	P	O	N	M	L	K
row 5	Z	Y	X	W	V	U	T	S
row 6	F3	F2	F1	CODE	CAPS	GRAPH	CTRL	SHIFT
row 7	RET	SELECT	BS	STOP	TAB	ESC	F5	F4
row 8	→	↓	↑	←	DEL	INS	HOME	SPACE
row 9	NUM4	NUM3	NUM2	NUM1	NUM0	NUM/	NUM+	NUM*
row 10	NUM.	NUM,	NUM-	NUM9	NUM8	NUM7	NUM6	NUM5

The MSX1 VDP

The MSX1 VDP has 16 KB of memory

The Tile Pattern definitions use 1 byte per line for 1 bit pixel data, and 1 byte per line in the Colormap area to define color, one nibble for Foreground, and one nibble for background, in the format &FB

The Tilemap has 2 modes... normal mode uses 256 definitions, in the area &0000-&07FF...

Alternate mode uses 3 Pattern definitions, one for the first 1/3rd of the screen, another for the 2nd 3rd, and the final for the last 3rd... this allows us to simualte a bitmap screen, as we have enough tiles for each block of the screen to be unique, while only having one byte per tile in the tilemap!

From	To	Meaning
0000	07FF	VRAM: Main Tile Patterns (1/3)
0800	0FFF	VRAM: Extra Tile Patterns (2/3)
1000	17FF	VRAM: Extra Tile Patterns (3/3)
1800	1AFF	VRAM: Tilemap
1B00	1B7F	VRAM: Sprite Attributes
1B80	1BAF	VRAM: Palette Table
2000	37FF	VRAM: Colormap
3800	3FFF	VRAM: Sprite Patterns

The color palette is fixed, and there are no brightness or other limitations (unlike the speccy!)

0	1	2	3	4	5	6	7
8	9	A	B	C	D	E	F

Note: Color 0 is transparent.

MSX1 Sprites
the MSX1 is capable of 32 onscreen sprites (max 4 on one line), that are 8x8 or 16x16 pixel size, each is one single color(not one color per line)
By default Sprite patterns are held at &3800 - there is enough ram for 64 16x16 sprite patterns, or 256 8x8 sprites.

Reg	Meaning	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
R#1	mode register #1	0	BL	IE0	M1	M2	0	SI	MAG	SI=16x16 sprites / MAG = Big Sprites
R#5	sprite attribute table (LOW)	A14	A13	A12	A11	A10	A9	A8	A7
R#6	sprite pattern generator table	0	0	A16	A15	A14	A13	A12	A11
R#8	mode register #2	MS	LP	TP	CB	VR	0	SPD	BW

SI in R#1 is the Spritesize 0=8x8 1=16x16
MAG in R#1 will double the size of the sprites
SPD in R#8 will DISABLE the sprites - if this is set sprites will not work!
R#5 is the address of the sprite bitmap data
R#6 is the address of the sprite attributes

MSX1 Sprite Attributes

Address	Sprite	Bits	Details
$1B00	0	YYYYYYYY	Y=Ypos
$1B01	0	XXXXXXXX	X=Xpos
$1B02	0	PPPPPPPP	P=Patternnum
$1B03	0	E---CCCC	E=Extended (Bit 8 of Xpos) C=Color
$1B04	1	YYYYYYYY	Y=Ypos
$1B05	1	XXXXXXXX	X=Xpos
$1B06	1	PPPPPPPP	P=Patternnum
$1B07	1	E---CCCC	E=Extended (Bit 8 of Xpos) C=Color
..	..	..	. .
$1B7C	31	YYYYYYYY	Y=Ypos
$1B7D	31	XXXXXXXX	X=Xpos
$1B7E	31	PPPPPPPP	P=Patternnum
$1B7F	31	E---CCCC	E=Extended (Bit 8 of Xpos) C=Color

The position and bitmap data of MSX1 sprites is defined by the attribute table, each sprite has 4 attributes...

Note the sepecial 'E' attribute in byte 4... this allows a sprite to be 'further left' than X=0 for sprites going off the left hand side of the screen

Pattern number can be from 0-255 for 8x8 tile mode....
for 16x16 tile mode it is 0-63...
NOTE... the 8x8 tiles need to be in a different order for this mode... imagine 4 8x8 blocks in a 16x16 sprite... they need to be in the following order:p

1	3
2	4

There is a special exporter in AkuSprite editor called 'Save RAW MSX1 16x16 Sprite'

The MSX2 VDP
The MSX2 GPU has to be controlled via it's ports via OUT commands.

MSX 2 - V9938 Ports

Port

When Read

When Written

&98

Read Data

Write Data

&99

Status

Control

&9A

Palette (use R#16 to select Palette entry)

&9B

Indirect register

V9990

Port	When Read	When Written
&60	Read Data	Write Data
&61		Palette
&62		Command
&63		Regsiter Data
&64		Register Select
&65	Status
&66	Interrupt Flag
&67		System
&6F		Superimpose

To control the MSX2 GPU, we have to set it's registers, and then send a command to register 46

To Set a register, first send the value to put in the register to the control port, then send the register number +128 to the control port.

EG lets set Reg 15 to 2...
    ld a,2
    out (&99),a
    ld a,15+128
    out (&99)dd
28 is an instruction meaning 'This is a register number'
Some registers like R#14 need more than 1 byte, just send these after the 14+128 command has been sent - the VDP will be expecting the extra data!

V9938 (MSX2) - Ports, Registers and Commands

Commands

Name	Command	From	To	Units	ByteCode	Function (USE)
HMMC	High Spd Move	CPU	VRAM	bytes	%11110000 (&F0)	Fill Bytes from OUTI (Define Sprites / CPU render)
YMMM	High Spd MoveY	VRAM	VRAM	bytes	%11100000 (&E0)	Copy an area from Vram to Vram only changing Y (Draw Background / Vscroll)
HMMM	High Spd Move	VRAM	VRAM	bytes	%11010000 (&D0)	Copy an area from Vram to Vram fast (blit Sprites / Scroll)
HMMV	High Spd Move	VDP	VRAM	bytes	%11000000 (&C0)	Fast fill a square with a single byte (Clear Areas)
LMMC	Logical Move	CPU	VRAM	dots	%10110000 (&B0)
LMCM	Logical Move	VRAM	CPU	dots	%10100000 (&A0)
LMMM	Logical Move	VRAM	VRAM	dots	%10010000 (&90)	Copy an area of Vram with Logical conditions (Transparency)
LMMV	Logical Move	VDP	VRAM	dots	%10000000 (&80)
LINE	Line	VDP	VRAM	dots	%01110000 (&70)
SRCH	Search	VDP	VRAM	dots	%01100000 (&60)
PSET	Pset	VDP	VRAM	dots	%01010000 (&50)
POINT	Point	VDP	VRAM	dots	%01000000 (&40)
STOP	Stop				%00000000 (&00)	Stop processing current task

If you want to know all the details, you should download the v9938 documentation here

Status Registers

Reg	Meaning	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
S#0	Status 0	F	5S	C	5SN	5SN	5SN	5SN	5SN
S#1	Status 1	FL	LPS	ID	ID	ID	ID	ID	FH
S#2	Status 2	TR	VR	HR	BD	1	1	EO	CE
S#3	Status 3	X7	X6	X5	X4	X3	X2	X1	X0
S#4	Status 4	1	1	1	1	1	1	1	X8
S#5	Status 5	Y7	Y6	Y5	Y4	Y3	Y2	Y1	Y0
S#6	Status 6	1	1	1	1	1	1	Y9	Y8
S#7	Status 7	C7	C6	C5	C4	C3	C2	C1	C0
S#8	Status 8	BX7	BX6	BX5	BX4	BX3	BX2	BX1	BX0
S#9	Status 9	1	1	1	1	1	1	1	BX8

Note:
The firmware expects status register S#0 to be selected in R#15

Interrupts will fire until S#0 is read... so you must do this if you write your own interrupt handler!

Registers ... MSX1 MSX2 MSX2+

Reg	Meaning	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
R#0	mode register #0	0	DG	IE2	IE1	M5	M4	M3	0
R#1	mode register #1 (IE0= IM1 on)	0	BL	IE0	M1	M2	0	SI	MAG
R#2	pattern name table	0	A16	A15	A14	A13	A12	A11	A10
R#3	color table (LOW)	A13	A12	A11	A10	A9	A8	A7	A6
R#4	pattern generator table	0	0	A16	A15	A14	A13	A12	A11
R#5	sprite attribute table (LOW)	A14	A13	A12	A11	A10	A9	A8	A7
R#6	sprite pattern generator table	0	0	A16	A15	A14	A13	A12	A11
R#7	border color/character color at text mode	TC3	TC2	TC1	TC0	BD3	BD2	BD1	BD0
R#8	mode register #2	MS	LP	TP	CB	VR	0	SPD	BW
R#9	mode register #3	LN	0	S1	S0	IL	E0	*NT	DC
R#10	color table (HIGH)	0	0	0	0	0	A16	A15	A14
R#11	sprite attribute table (HIGH)	0	0	0	0	0	0	A16	A15
R#12	character color at text blinks	T23	T22	T21	T20	BC3	BC2	BC1	BC0
R#13	blinking period	ON3	ON2	ON1	ON0	OF3	OF2	OF1	OF0
R#14	VRAM access address (HIGH)	0	0	0	0	0	A16	A15	A14
		A7	A6	A5	A4	A3	A2	A1	A0
		0	RW	A13	A12	A11	A10	A9	A8
R#15	indirect specification of S#n	0	0	0	0	S3	S2	S1	S0
R#16	indirect specification of P#n (Palette)	0	0	0	0	C3	C2	C1	C0
R#17	indirect specification of R#n	AII	0	R5	R4	R3	R2	R1	R0
R#18	screen location adjustment (ADJUST) (Scroll)	V3	V2	V1	V0	H3	H2	H1	H0
R#19	scanning line number when the interrupt occurs	IL7	IL6	IL5	IL4	IL3	IL2	IL1	IL0
R#20	color burst signal 1	0	0	0	0	0	0	0	0
R#21	color burst signal 2	0	0	1	1	1	0	1	1
R#22	color burst signal 3	0	0	0	0	0	1	0	1
R#23	screen hard V-scroll	DO7	DO6	DO5	DO4	DO3	DO2	DO1	DO0
R#25	Scroll Options (left side Mask / 2 page)	0	0	0	0	0	0	MSK	SP2
R#26	Screen H-scroll (Bits 8-3)	0	0	H08	H07	H06	H05	H04	H03
R#27	Screen H-scroll (Bits 2-0)	0	0	0	0	0	H02	H01	H00
R#32	SX: X-coordinate to be transferred (LOW)	SX7	SX6	SX5	SX4	SX3	SX2	SX1	SX0
R#33	SX: X-coordinate to be transferred (HIGH)	0	0	0	0	0	0	0	SX8
R#34	SY: Y-coordinate to be transferred (LOW)	SY7	SY6	SY5	SY4	SY3	SY2	SY1	SY0
R#35	SY: Y-coordinate to be transferred (HIGH)	0	0	0	0	0	0	SY9	SY8
R#36	DX: X-coordinate to be transferred to (LOW)	DX7	DX6	DX5	DX4	DX3	DX2	DX1	DX0
R#37	DX: X-coordinate to be transferred to (HIGH)	0	0	0	0	0	0	0	DX8
R#38	DY: Y-coordinate to be transferred to (LOW)	DY7	DY6	DY5	DY4	DY3	DY2	DY1	DY0
R#39	DY: Y-coordinate to be transferred to (HIGH)	0	0	0	0	0	0	DY9	DY8
R#40	NX: num. of dots to be transferred in X direction (LOW)	NX7	NX6	NX5	NX4	NX3	NX2	NX1	NX0
R#41	NX: num. of dots to be transferred in X direction (HIGH)	0	0	0	0	0	0	0	NX8
R#42	NY: num. of dots to be transferred in Y direction (LOW)	NY7	NY6	NY5	NY4	NY3	NY2	NY1	NY0
R#43	NY: num. of dots to be transferred in Y direction (HIGH)	0	0	0	0	0	0	NY9	NY8
R#44	CLR: for transferring data to CPU	-	-	-	-	C3	C2	C1	C0
		-	-	-	-	-	C1	C0	G5
		C7	C6	C5	C4	C3	C2	C1	C0
R#45	ARG: bank switching between VRAM and expanded VRAM Comparison (EQ) / Draw Direction (MAJ)	0	MXC	MXD	MXS	DIY	DIX	EQ	MAJ
R#46	CMR: send VDP command	CMD	CMD	CMD	CMD	MSK	MSK	MSK	MSK

Masks (R46 bits 0-3)

Code	Function	Bits
IMP	PSET	%0000 (&00)
AND	Mask	%0001 (&01)
OR		%0010 (&02)
XOR	XOR draw	%0011 (&03)
NOT		%0100 (&00)

TIMP	Color 0 = Transparent	%1000 (&08)
TAND		%1001 (&09)
TOR		%1010 (&0A)
TXOR		%1011 (&0B)
TNOT		%1100 (&0C)

Draw Direction (R45 bits 2/3)

Direction	Bits
DownRight	%00 (&00)
DownLeft	%01 (&04)
UpRight	%10 (&08)
UpLeft	%11 (&0C)

V9938 (MSX2) Command/Register usage

		HMMC (Define)	HMMV (Fill)	HMMM (Draw sprite)	LMMM (Draw Transp)
	First Used Register:	36	36	32	32
R#32	SX: X-coordinate to be transferred (LOW)			SX-L	SX-L
R#33	SX: X-coordinate to be transferred (HIGH)			SX-H	SX-H
R#34	SY: Y-coordinate to be transferred (LOW)			SY-L	SY-L
R#35	SY: Y-coordinate to be transferred (HIGH)			SY-H	SY-H
R#36	DX: X-coordinate to be transferred to (LOW)	DX-L	DX-L	DX-L	DX-L
R#37	DX: X-coordinate to be transferred to (HIGH)	DX-H	DX-H	DX-H	DX-H
R#38	DY: Y-coordinate to be transferred to (LOW)	DY-L	DY-L	DY-L	DY-L
R#39	DY: Y-coordinate to be transferred to (HIGH)	DY-H	DY-H	DY-H	DY-H
R#40	NX: num. of dots to be transferred in X direction (LOW)	Width-L	Width-L	Width-L	Width-L
R#41	NX: num. of dots to be transferred in X direction (HIGH)	Width-H	Width-H	Width-H	Width-H
R#42	NY: num. of dots to be transferred in Y direction (LOW)	Height-L	Height-L	Height-L	Height-L
R#43	NY: num. of dots to be transferred in Y direction (HIGH)	Height-H	Height-H	Height-H	Height-H
R#44	CLR: for transferring data to CPU	FirstByte	-	-	-
R#45	ARG: bank switching between VRAM and expanded VRAM	0	0	0	0
R#46	CMR: send VDP command	&F0	&C0	&D0	&98 (8=TIMP)

Fields marked - can be anything / Empty fields do not need setting

V9990 - Ports, Registers and Commands

V9990 Commands

Name	Command	From	To	Units	ByteCode	Function
STOP	Stop				%00000000	Stop processing current task
LMMC	Logical Move	CPU	VRAM		%00010000	Fill Bytes from OUTI
LMMV	Logical Move	VDP	VRAM		%00100000	Flood fill a square with a single byte
LMCM	Logical Move	VRAM	CPU		%00110000
LMMM	Logical Move	VRAM	VRAM	dots	%01000000	Copy an area from Vram to Vram fast (blit)
CMMC	Color-Develop	CPU	VRAM		%01010000

CMMM	Color-Develop	VRAM	VRAM		%01110000
BMXL	Linear BMP	L-VRAM	VRAM		%10000000
BMLX	Linear BMP	VRAM	L-VRAM		%10010000
BMLL	Linear BMP	L-VRAM	L-VRAM		%10100000
LINE	Line				%10110000
SEARCH	Search				%11000000
POINT	Point				%11010000
PSET	Pset				%11100000
ADVANCE					%11110000

If you want to know all the details, you should download the v9938 documentation here

V9990 Status

Reg	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
Port &65	TR	VR	HR	BD	0	MCS	EO	CE

Check CE to see if VDP is busy...

Note:
Even if you:re using the VDP, you need to check the MSX status port in your interrupt handler as usual!

V9990 Registers

Reg	Meaning	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
R#0	Vram Write L	L	L	L	L	L	L	L	L
R#1	Vram Write H	H	H	H	H	H	H	H	H
R#2	Vram Write X	X	X	X	X	X	X	X	X
R#3	Vram Read L	L	L	L	L	L	L	L	L
R#4	Vram Read H	H	H	H	H	H	H	H	H
R#5	Vram Read X	X	X	X	X	X	X	X	X
R#6	Screen Mode	D	D	C	C	X	X	B	B
R#7	Screen Mode
R#8	Control	D	S	Y	S	W	0	1	0
R#9	Interrupt
R#10	Interrupt
R#11	Interrupt
R#12	Interrupt
R#13	Palette Control
R#14	Palette Pointer (autoinc)	Num	Num	Num	Num	Num	Num	Chn	Chn
R#15	Back drop color	-	-	B	B	B	B	B	B
R#16	Display Adjust	V	V	V	V	H	H	H	H
R#17	Scroll Control
R#18	Scroll Control
R#19	Scroll Control
R#20	Scroll Control
R#21	Scroll Control
R#22	Scroll Control
R#23	Scroll Control
R#24	Scroll Control
R#25	Sprite Generator Base Address
R#26	LCD Control
R#27	Priority Control
R#28	Cursor Sprite Palette Offset
R#32	SX L	L	L	L	L	L	L	L	L
R#33	SX H	H	H	H	H	H	H	H	H
R#34	SY L	L	L	L	L	L	L	L	L
R#35	SY H	H	H	H	H	H	H	H	H
R#36	DX L	L	L	L	L	L	L	L	L
R#37	DX H	H	H	H	H	H	H	H	H
R#38	DY L	L	L	L	L	L	L	L	L
R#39	DY H	H	H	H	H	H	H	H	H
R#40	NX L	L	L	L	L	L	L	L	L
R#41	NX H	H	H	H	H	H	H	H	H
R#42	NY L	L	L	L	L	L	L	L	L
R#43	NY H	H	H	H	H	H	H	H	H
R#44	Move	0	0	0	0	DIY	DIX	NEQ	NAJ
R#45	Logical Operation	0	0	0	TP	L11	L10	L01	L00
R#46	Write Mask L	L	L	L	L	L	L	L	L
R#47	Write Mask H	H	H	H	H	H	H	H	H
R#48	Foreground Font Color L	L	L	L	L	L	L	L	L
R#49	Foreground Font Color H	H	H	H	H	H	H	H	H
R#50	Background Font Color L	L	L	L	L	L	L	L	L
R#51	Background Font Color H	H	H	H	H	H	H	H	H
R#52	Operation Code	C	C	C	C	-	-	-	-
R#53	Search Command	B	B	B	B	B	B	B	B
R#54	Search Command	-	-	-	-	-	B	B	B

AY Sound Chip:

Register	Meaning	Bit Meaning	Details
0	Tone Pitch L - Channel A	LLLLLLLL	Lower value = Higher pitch
1	Tone Pitch H - Channel A	----HHHH	Lower value = Higher pitch
2	Tone Pitch L - Channel B	LLLLLLLL	Lower value = Higher pitch
3	Tone Pitch H - Channel B	----HHHH	Lower value = Higher pitch
4	Tone Pitch L - Channel C	LLLLLLLL	Lower value = Higher pitch
5	Tone Pitch H - Channel C	----HHHH	Lower value = Higher pitch
6	Noise Generator	---NNNNN	Higer = Faster noise
7	Mixer	--NNNTTT	N=Noise T=Tone (Channel --CBACBA 1=mute 0=normal)
8	Amplitude - Channel A	---EVVVV	E=Envelope (1=Enabled) VVVV=Volume
9	Amplitude - Channel B	---EVVVV	E=Envelope (1=Enabled) VVVV=Volume
10	Amplitude - Channel C	---EVVVV	E=Envelope (1=Enabled) VVVV=Volume
11	Envelope L (Volume over time)	LLLLLLLL	Lower=Faster Envelope
12	Envelope H (Volume over time)	HHHHHHHH	Lower=Faster Envelope
13	Envelope Selection	----EEEE	Envelope number (See PDF)

For more details, please see the AY sound chip PDF

Ram Variables:

Section	Address	Name	Details
Rom	0000H	CHKRAM	RST0: tests RAM and sets RAM slot for the system
	0008H	SYNCHR	RST1: tests whether the character of [HL] is the specified
	000CH	RDSLT	selects the slot corresponding to the value of A and reads
	0010H	CHRGTR	RST2: gets a character or a token from BASIC text
	0014H	WRSLT	selects the slot corresponding to the value of A and writes one byte
	0018H	OUTDO	RST3: sends the value to current device
	001CH	CALSLT	calls the routine in another slot inter-slot call
	0020H	DCOMPR	RST4: compares the contents of HL and DE
	0024H	ENASLT	selects the slot corresponding to the value of A and enables the slot to be used
	0028H	GETYPR	RST5: returns the type of DAC decimal accumulator
	0030H	CALLF	RST6: calls the routine in another slot.
	0038H	KEYINT	RST7: executes the timer interrupt process routine
	003BH	INITIO	initialises the device
	003EH	INIFNK	initialises the contents of function keys
	0041H	DISSCR	inhibits the screen display
	0044H	ENASCR	displays the screen
	0047H	WRTVDP	writes data in the VDP register
	004AH	RDVRM	reads the contents of VRAM.
	004DH	WRTVRM	writes data in VRAM
	0050H	SETRD	sets VRAM address to VDP and enables it to be read.
	0053H	SETWRT	sets VRAM address to VDP and enables it to be written.
	0056H	FILVRM	fills the specified VRAM area with the same data.
	0059H	LDIRMV	block transfer from VRAM to memory
	005CH	LDIRVM	block transfer from memory to VRAM
	005FH	CHGMOD	changes the screen mode. The palette is not initialised.
	0062H	CHGCLR	changes the screen color
	0066H	NMI	executes NMI Non-Maskable Interrupt handling routine
	0069H	CLRSPR	initialises all sprites.
	006CH	INITXT	initialises the screen to TEXT1 mode 40 x 24
	006FH	INIT32	initialises the screen to GRAPHIC1 mode 32x24
	0072H	INIGRP	initialises the screen to the high-resolution graphics mode.
	0075H	INIMLT	initialises the screen to MULTI color mode.
	0078H	SETTXT	set only VDP in TEXT1 mode 40x24
	007BH	SETT32	set only VDP in GRAPHIC1 mode 32x24
	007EH	SETGRP	set only VDP in GRAPHIC2 mode
	0081H	SETMLT	set only VDP in MULTI color mode
	0084H	CALPAT	returns the address of the sprite generator table
	0087H	CALATR	returns the address of the sprite attribute table
	008AH	GSPSIZ	returns the current sprite size
	008DH	GRPPRT	displays a character on the graphic screen
	0090H	GICINI	initialises PSG and sets the initial value for the PLAY statement
	0093H	WRTPSG	writes data in the PSG register
	0096H	RDPSG	reads the PSG register value
	0099H	STRTMS	tests whether the PLAY statement is being executed as a background task.
	009CH	CHSNS	tests the status of the keyboard buffer
	009FH	CHGET	one character input waiting
	00A2H	CHPUT	displays the character
	00A5H	LPTOUT	sends one character to the printer
	00A8H	LPTSTT	tests the printer status
	00ABH	CNVCHR	test for the graphic header and transforms the code
	00AEH	PINLIN	stores in the specified buffer the character codes input till STOP key.
	00B1H	INLIN	same as PINLIN except that AUTFLG F6AAH is set
	00B4H	QINLIN	executes INLIN with displaying "?" and one space
	00B7H	BREAKX	tests Ctrl-STOP key. In this routine, interrupts are inhibited.
	00C0H	BEEP	generates BEEP
	00C3H	CLS	clears the screen
	00C6H	POSIT	moves the cursor
	00C9H	FNKSB	tests whether the function key display is active FNKFLG
	00CCH	ERAFNK	erases the function key display
	00CFH	DSPFNK	displays the function keys
	00D2H	TOTEXT	forces the screen to be in the text mode
	00D5H	GTSTCK	returns the joystick status
	00D8H	GTTRIG	returns the trigger button status
	00DBH	GTPAD	returns the touch pad status
	00DEH	GTPDL	returns the paddle value
	00E1H	TAPION	reads the header block after turning the cassette motor ON.
	00E4H	TAPIN	reads data from the tape
	00E7H	TAPIOF	stops reading the tape
	00EAH	TAPOON	writes the header block after turning the cassette motor ON
	00EDH	TAPOUT	writes data on the tape
	00F0H	TAPOOF	stops writing to the tape
	00F3H	STMOTR	sets the cassette motor action
	0132H	CHGCAP	alternates the CAP lamp status
	0135H	CHGSND	alternates the 1-bit sound port status
	0138H	RSLREG	reads the contents of current output to the basic slot register
	013BH	WSLREG	writes to the primary slot register
	013EH	RDVDP	reads VDP status register
	0141H	SNSMAT	reads the value of the specified line from the keyboard matrix
	0144H	PHYDIO	Physical input/output for disk devices
	014AH	ISFLIO	tests whether the device is active
	014DH	OUTDLP	printer output
	0156H	KILBUF	clears the keyboard buffer
	0159H	CALBAS	executes inter-slot call to the routine in BASIC interpreter
MSX2	015CH	SUBROM	executes inter-slot call to SUB-ROM
	015FH	EXTROM	executes inter-slot call to SUB-ROM
	0168H	EOL	deletes to the end of the line
	016BH	BIGFIL	same function as FILVRM.
	016EH	NSETRD	enables VRAM to be read by setting the address
	0171H	NSTWRT	enables VRAM to be written by setting the address
	0174H	NRDVRM	reads the contents of VRAM
	0177H	NWRVRM	writes data in VRAM
Sub-Rom	0089H	GRPRT	one character output to the graphic screen active only in screen modes 5 to 8
	00C9H	NVBXLN	draws a box
	00CDH	NVBXFL	draws a painted box
	00D1H	CHGMOD	changes the screen mode
	00D5H	INITXT	initialises the screen to TEXT1 mode 40 x 24
	00D9H	INIT32	initialises the screen to GRAPHIC1 mode 32x24
	00DDH	INIGRP	initialises the screen to the high-resolution graphics mode
	00E1H	INIMLT	initialises the screen to MULTI color mode
	00E5H	SETTXT	sets VDP in the text mode 40x24
	00E9H	SETT32	ses VDP in the text mode 32x24
	00EDH	SETGRP	sets VDP in the high-resolution mode
	00F1H	SETMLT	sets VDP in MULTI color mode
	00F5H	CLRSPR	initialises all sprites.
	00F9H	CALPAT	returns the address of the sprite generator table
	00FDH	CALATR	returns the address of the sprite attribute table
	0101H	GSPSIZ	returns the current sprite size
	0105H	GETPAT	returns the character pattern
	0109H	WRTVRM	writes data in VRAM
	010DH	RDVRM	reads the contents of VRAM
	0111H	CHGCLR	changes the screen color
	0115H	CLSSUB	clears the screen
	011DH	DSPFNK	displays the function keys
	012DH	WRTVDP	writes data in the VDP register
	0131H	VDPSTA	reads the VDP register
	013DH	SETPAG	switches the page
	0141H	INIPLT	initialises the palette(the current palette is saved in VRAM
	0145H	RSTPLT	restores the palette from VRAM
	0149H	GETPLT	obtains the color code from the palette
	014DH	SETPLT	sets the color code to the palette
	017DH	BEEP	generates BEEP
	0181H	PROMPT	displays the prompt
	01ADH	NEWPAD	reads the status of mouse or light pen
	01B5H	CHGMDP	changes VDP mode. The palette is initialised.
	01BDH	KNJPRT	sends a kanki to the graphic screen modes 5 to 8
	01F5H	REDCLK	reads the clock data
	01F9H	WRTCLK	writes the clock data
Interslot	F380H	RDPRIM	read from basic slot
	F385H	WRPRIM	write to basic slot
	F38CH	CLPRIM	basic slot call
USR	F39AH	USRTAB	initial value: FCERR contents: starting address of assembly language program of USR function 0 to 9 ; the value before defining assembly language program
	F3AEH	LINL40	initial value: 39 contents: screen width per line at SCREEN 0 set by WIDTH statement at SCREEN 0
	F3AfH	LINL32	initial value: 32 contents: screen width per line at SCREEN 1 set by WIDTH statement at SCREEN 1
	F3B0H	LINLEN	initial value: 29 contents: current screen width per line
	F3B1H	CRTCNT	initial value: 24 contents: number of lines of current screen
	F3B2H	CLMLST	initial value: 14 contents: horizontal location in the case that items are divided by commas in PRINT statement
Screen 0	F3B3H	TXTNAM	initial value: 0000H contents: pattern name table
	F3B5H	TXTCOL	contents: unused
	F3B7H	TXTCGP	initial value: 0800H contents: pattern generator table
	F3B9H	TXTATR	contents: unused
	F3BBH	TXTPAT	contents: unused
Screen 1	F3BDH	T32NAM	initial value: 1800H contents: pattern name table
	F3BFH	T32COL	initial value: 2000H contents: color table
	F3C1H	T32CGP	initial value: 0000H contents: pattern generator table
	F3C3H	T32ATR	initial value: 1B00H contents: sprite attribute table
	F3C5H	T32PAT	initial value: 3800H contents: sprite generator table
Screen 2	F3C7H	GRPNAM	initial value: 1800H contents: pattern name table
	F3C9H	GRPCOL	initial value: 2000H contents: color table
	F3CBH	GRPCGP	initial value: 0000H contents: pattern generator table
	F3CDH	GRPATR	initial value: 1B00H contents: sprite attribute table
	F3CFH	GRPPAT	initial value: 3800H contents: sprite generator table
Screen 3	F3D1H	MLTNAM	initial value: 0800H contents: pattern name table
	F3D3H	MLTCOL	contents: unused
	F3D5H	MLTCGP	initial value: 0000H contents: pattern generator table
	F3D7H	MLTATR	initial value: 1B00H contents: sprite attribute table
	F3D9H	MLTPAT	initial value: 3800H contents: sprite generator table
Screen Extra	F3DBH	CLIKSW	initial value: 1 contents: key click switch 0 = OFF, otherwise = ON , set by <key click switch> of SCREEN statement
	F3DCH	CSRY	initial value: 1 contents: Y-coordinate of cursor
	F3DDH	CSRX	initial value: 1 contents: X-coordinate of cursor
	F3DEH	CNSDFG	initial value: 0 contents: function key display switch 0 = display, otherwise = no display , set by KEY ON/OFF statement
VDP bak	F3DFH	RG0SAV	initial value: 0
	F3E0H	RG1SAV	initial value: E0H
	F3E1H	RG2SAV	initial value: 0
	F3E2H	RG3SAV	initial value: 0
	F3E3H	RG4SAV	initial value: 0
	F3E4H	RG5SAV	initial value: 0
	F3E5H	RG6SAV	initial value: 0
	F3E6H	RG7SAV	initial value: 0
	F3E7H	STATFL	initial value: 0 contents: stores VDP status contents of status register 0, in MSX2
	F3E8H	TRGFLG	initial value: FFH contents: stores trigger button status of joystick
	F3E9H	FORCLR	initial value: 15 contents: foreground color; set by color statement
	F3EAH	BAKCLR	initial value: 4 contents: background color; set by color statement
	F3EBH	BDRCLR	initial value: 7 contents: border color; set by color statement
	F3ECH	MAXUPD	initial value: JP 0000H C3H, 00H, 00H contents: used by CIRCLE statement internally
	F3EFH	MINUPD	initial value: JP 0000H C3H, 00H, 00H contents: used by CIRCLE statement internally
	F3F2H	ATRBYT	initial value: 15 contents: color code in using graphics
PLAY	F3F3H	QUEUES	initial value: QUETAB F959H contents: points to queue table at the execution of PLAY statement
	F3F5H	FRCNEW	, 1 initial value: 255 contents: used by BASIC interpreter internally
Key Input	F3F6H	SCNCNT	initial value: 1 contents: interval for the key scan
	F3F7H	REPCNT	initial value: 50 contents: delay until the auto-repeat of the key begins
	F3F8H	PUTPNT	initial value: KEYBUF FBF0H contents: points to address to write in the key buffer
	F3FAH	GETPNT	initial value: KEYBUF FBF0H contents: points to address to read from key buffer
Casette	F3FCH	CS120	- 1200 baud contents: 83 LOW01 ............ Low width representing bit 0
	F406H	LOW	initial value: LOW01, HIGH01 by default, 1200 baud contents: width of LOW and HIGH which represents bit 0 of current baud rate; set by <cassette baud rate> of SCREEN statement
	F408H	HIGH	initial value: LOW11, HIGH11 by default, 1200 baud contents: width of LOW and HIGH which represents bit 1 of current baud rate; set by <cassette baud rate> of SCREEN statement
	F40AH	HEADER	initial value: HEADLEN * 2/256 by default, 1200 baud contents: header bit for the short header of current baud rate HEADLEN = 2000
	F40BH	ASPCT1	contents: 256/aspect ratio; set by SCREEN statement to use in CIRCLE statement
	F40DH	ASPCT2	contents: 256 * aspect ratio; set by SCREEN statement to use in CIRCLE statement
	F40FH	ENDPRG	initial value: ":" contents: false end of program for RESUME NEXT statement
BASIC	F414H	ERRFLG	area to store the error number
	F415H	LPTPOS	initial value: 0 contents: printer head location
	F416H	PRTFLG	flag whether to send to printer
	F417H	NTMSXP	printer 0 = printer for MSX, otherwise not
	F418H	RAWPRT	non-zero when printing in raw-mode
	F419H	VLZADR	address of character to be replaced by VAL function
	F41BH	VLZDAT	character to be replaced with 0 by VAL function
	F41CH	CURLIN	currently executing line number of BASIC
	F41FH	KBUF	crunch buffer; translated into intermediate language from BUF F55EH
	F55DH	BUFMIN	initial value: "," contents: used in INPUT statement
	F55EH	BUF	buffer to store characters typed; where direct statements are stored in ASCII code
	F660H	ENDBUF	prevents overflow of BUF F55EH
	F661H	TTYPOS	virtual cursor location internally retained by BASIC
	F662H	DIMFLG	used by BASIC internally
	F663H	VALTYP	used to identify the type of variable
	F664H	DORES	indicates whether stored word can be crunched
	F665H	DONUM	flag for crunch
	F666H	CONTXT	stores text address used by CHRGET
	F668H	CONSAV	stores token of constant after calling CHRGET
	F669H	CONTYP	type of stored constant
	F66AH	CONLO	value of stored constant
	F672H	MEMSIZ	highest address of memory used by BASIC
	F674H	STKTOP	address used as stack by BASIC; depending on CLEAR statement
	F676H	TXTTAB	starting address of BASIC text area
	F768H	TEMPPT	initial value: TEMPST F67AH contents: starting address of unused area of temporary descriptor
	F67AH	TEMPST	area for NUMTEMP
	F698H	DSCTMP	string descriptor which is the result of string function
	F69BH	FRETOP	starting address of unused area of string area
	F69DH	TEMP3	used for garbage collection or by USR function
	F69FH	TEMP8	for garbage collection
	F6A1H	ENDFOR	stores next address of FOR statement to begin execution from the next of FOR statement at loops
	F6A3H	DATLIN	line number of DATA statement read by READ statement
	F6A5H	SUBFLG	flag for array for USR function
	F6A6H	FLGINP	flag used in INPUT or READ
	F6A7H	TEMP	location for temporary reservation for statement code; used for variable pointer, text address, and others
	F6A9H	PTRFLG	0 if there is not a line number to be converted,otherwise not
	F6AAH	AUTFLG	flag for AUTO command validity non-zero = valid, otherwise invalid
	F6ABH	AUTLIN	last input line number
	F6ADH	AUTINC	initial value: 10 contents: increment value of line number of AUTO command
	F6AFH	SAVTXT	area to store address of currently executing text; mainly used for error recovery by RESUME statement
	F6B3H	ERRLIN	line number where an error occurred
	F6B5H	DOT	last line number which was displayed in screen or entered
	F6B7H	ERRTXT	text address which caused an error; mainly used for error recovery by RESUME statement
	F6B9H	ONELIN	text address to which control jumps at error; set by ON ERROR GOTO statement
	F6BBH	ONEFLG	flag which indicates error routine execution non-zero = in execution, otherwise not
	F6BCH	TEMP2	for temporary storage
	F6BEH	OLDLIN	line number which was terminated by Ctrl+STOP, STOP instruction, END instruction, or was executed last
	F6C0H	OLDTXT	address to be executed next
	F6C2H	VARTAB	starting address of simple variable; executing NEW statement causes [contents of TXTTAB(F676H + 2] to be set
	F6C4H	ARYTAB	starting address of array table
	F6C6H	STREND	last address of memory in use as text area or variable area
	F6C8H	DATPTR	text address of data read by executing READ statement
	F6CAH	DEFTBL	area to store type of variable for one alphabetical character; depends on type declaration such as CLEAR, DEFSTR,!, or #
User Func	F6E4H	PRMSTK	previous definition block on stack for garbage collection
	F6E6H	PRMLEN	number of bytes of objective data
	F6E8H	PARM1	objective parameter definition table; PRMSIZ is number of bytes of definition block, initial value is 100
	F74CH	PRMPRV	initial value: PRMSTK contents: pointer to previous parameter block for garbage collection
	F74EH	PRMLN2	size of parameter block
	F750H	PARM2	for parameter storage
	F7B4H	PRMFLG	flag to indicate whether PARM1 was searched
	F7B5H	ARYTA2	end point of search
	F7B7H	NOFUNS	0 if there is not an objective function
	F7B8H	TEMP9	location of temporary storage for garbage collection
	F7BAH	FUNACT	number of objective functions
	F7BCH	SWPTMP	location of temporary storage of the value of the first variable of SWAP statement
	F7C4H	TRCFLG	trace flag non-zero = TRACE ON, 0 = TRACE OFF
Math Pack	F7C5H	FBUFFR	used internally by Math-Pack
	F7F0H	DECTMP	used to transform decimal integer to floating-point number
	F7F2H	DECTM2	used at division routine execution
	F7F4H	DECCNT	used at division routine execution
	F7F6H	DAC	area to set the value to be calculated
	F806H	HOLD8	register storage area for decimal multiplication
	F836H	HOLD2	used internally by Math-Pack
	F83EH	HOLD	used internally by Math-Pack
	F847H	ARG	area to set the value to be calculated with DAC F7F6H
	F857H	RNDX	stores last random number in double precision real number; set by RND function
Basic Interpreter	F85FH	MAXFIL	maximum file number; set by MAXFILES statement
	F860H	FILTAB	starting address of file data area
	F862H	NULBUF	points to buffer used in SAVE and LOAD by BASIC interpreter
	F864H	PTRFIL	address of file data of currently accessing file
	F866H	RUNFLG	non-zero value if program was loaded and executed; used by R option of LOAD statement
	F866H	FILNAM	area to store filename
	F871H	FILNM2	area to store filename
	F87CH	NLONLY	non-zero value if program is being loaded
	F87DH	SAVEND	end address of assembly language program to be saved
	F87FH	FNKSTR	area to store function key string 16 character x 10
	F91FH	CGPNT	address to store character font on ROM
	F922H	NAMBAS	base address of current pattern name table
	F924H	CGPBAS	base address of current pattern generator table
	F926H	PATBAS	base address of current sprite generator table
	F928H	ATRBAS	base address of current sprite attribute table
	F92AH	CLOC	used internally by graphic routine
	F92CH	CMASK	used internally by graphic routine
	F92DH	MINDEL	used internally by graphic routine
	F92FH	MAXDEL	used internally by graphic routine
Basic Circle	F931H	ASPECT	aspect ratio of the circle; set by <ratio> of CIRCLE statement
	F933H	CENCNT	used internally by CIRCLE statement
	F935H	CLINEF	flag whether a line is drawn toward the center; specified by <angle> of CIRCLE statement
	F936H	CNPNTS	point to be plotted
	F938H	CPLOTF	used internally by CIRCLE statement
	F939H	CPCNT	number of one eight of the circle
	F93BH	CPNCNT8	used internally by CIRCLE statement
	F93DH	CPCSUM	used internally by CIRCLE statement
	F93FH	CSTCNT	used internally by CIRCLE statement
	F941H	CSCLXY	scale of x and y
	F942H	CSAVEA	reservation area of ADVGRP
	F944H	CSAVEM	reservation area of ADVGRP
	F945H	CXOFF	x offset from the center
	F947H	CYOFF	y offset from the center
Basic Paint	F949H	LOHMSK	used internally by PAINT statement
	F94AH	LOHDIR	used internally by PAINT statement
	F94BH	LOHADR	used internally by PAINT statement
	F94DH	LOHCNT	used internally by PAINT statement
	F94FH	SKPCNT	skip count
	F951H	MIVCNT	movement count
	F953H	PDIREC	direction of the paint
	F954H	LFPROG	used internally by PAINT statement
	F955H	RTPROG	used internally by PAINT statement
Basic Play	F956H	MCLTAB	points to the top of the table of PLAY macro or DRAW macro
	F958H	MCLFLG	assignment of PLAY/DRAW
	F959H	QUETAB	queue table
	F971H	QUEBAK	used in BCKQ
	F975H	VOICAQ	queue of voice 1 (A)
	F9F5H	VOICBQ	queue of voice 2 (B)
	FA75H	VOICCQ	queue of voice 3 �
	FAF5H	DPPAGE	display page number
	FAF6H	ACPAGE	active page number
	FAF7H	AVCSAV	reserves AV control port
	FAF8H	EXBRSA	SUB-ROM slot address
	FAF9H	CHRCNT	character counter in the buffer; used in Roman-kana translation value is 0 <=n <=2
	FAFAH	ROMA	area to store character in the buffer; used in Roman-kana translation Japan version only
	FAFCH	MODE	mode switch for VRAM size
	FAFDH	NORUSE	unused
	FAFEH	XSAVE	[ I OOOOOOO XXXXXXXX ]
	FB00H	YSAVE	[ x OOOOOOO YYYYYYYY ]
	FB02H	LOGOPR	logical operation code
	FB03H	RSTMP	work area for RS-232C or disk
	FB03H	TOCNT	used internally by RS-232C routine
	FB04H	RSFCB	FB04H + 0: LOW address of RS-232C FB04H + 1: HIGH address of RS-232C
	FB06H	RSIQLN	used internally by RS-232C routine
	FB07H	MEXBIH	FB07H +0: RST 30H 0F7H
	FB0CH	OLDSTT	FB0CH +0: RST 30H 0F7H
	FB12H	OLDINT	FB12H +0: RST 30H 0F7H
	FB17H	DEVNUM	used internally by RS-232C routine
	FB18H	DATCNT	FB18H +0: byte data
	FB1BH	ERRORS	used internally by RS-232C routine
	FB1CH	FLAGS	used internally by RS-232C routine
	FB1DH	ESTBLS	used internally by RS-232C routine
	FB1EH	COMMSK	used internally by RS-232C routine
	FB1FH	LSTCOM	used internally by RS-232C routine
	FB20H	LSTMOD	used internally by RS-232C routine
DOS	FB21H to FB34H	reserved	used by DOS
PLAY	FB35H	PRSCNT	D1 to D0 string parse D7 = 0 1 pass
	FB36H	SAVSP	reserves stack pointer in play
	FB38H	VOICEN	current interpreted voice
	FB39H	SAVVOL	reserves volume for the pause
	FB3BH	MCLLEN	used internally by PLAY statement
	FB3CH	MCLPTR	used internally by PLAY statement
	FB3EH	QUEUEN	used internally by PLAY statement
	FC3FH	MUSICF	interrupt flag for playing music
	FB40H	PLYCNT	number of PLAY statements stored in the queue
Voice	FB41H	VCBA	static data for voice 0
	FB66H	VCBB	static data for voice 1
	FB8BH	VCBC	static data for voice 2
Data	FBB0H	ENSTOP	flag to enable warm start by [SHIFT+Ctrl+Kana key] 0 = disable, otherwise enable
	FBB1H	BASROM	indicates BASIC text location 0 = on RAM, otherwise in ROM
	FBB2H	LINTTB	line terminal table; area to keep information about each line of text screen
	FBCAH	FSTPOS	first character location of line from INLIN 00B1H of BIOS
	FBCCH	CODSAV	area to reserve the character where the cursor is stacked
	FBCDH	FNKSW1	indicates which function key is displayed at KEY ON
	FBCEH	FNKFLG	contents: area to allow, inhibit, or stop the execution of the line defined in ON KEY GOSUB statement, or to reserve it for each function key; set by KEY(n ON/OFF/STOP statement
	FBD8H	ONGSBF	flag to indicate whether event waiting in TRPTBL FC4CH occurred
	FBD9H	CLIKFL	key click flag
	FBDAH	OLDKEY	key matrix status old
	FBE5H	NEWKEY	key matrix status new
	FBF0H	KEYBUF	key code buffer
	FC18H	LINWRK	temporary reservation location used by screen handler
	FC40H	PATWRK	temporary reservation location used by pattern converter
	FC48H	BOTTOM	installed RAM starting low address; ordinarily 8000H in MSX2
	FC4AH	HIMEM	highest address of available memory; set by <memory upper limit> of CLEAR statement
	FC4CH	TRAPTBL	trap table used to handle interrupt; one table consists of three bytes, where first byte indicates ON/OFF/STOP status and the rest indicate the text address to be jumped to
	FC9AH	RTYCNT	used internally by BASIC
	FC9BH	INTFLG	if Ctrl+STOP is pressed, setting 03H here causes a stop
	FC9CH	PADY	Y-coordinate of the paddle
	FC9DH	PADX	X-coordinate of the paddle
	FC9EH	JIFFY	used internally by PLAY statement
	FCA0H	INTVAL	interval period; set by ON INTERVAL GOSUB statement
	FCA2H	INTCNT	counter for interval
	FCA4H	LOWLIM	used during reading from cassette tape
	FCA5H	WINWID	used during reading from cassette tape
	FCA6H	GRPHED	flag to send graphic character 1 = graphic character, 0 = normal character
	FCA7H	ESCCNT	area to count from escape code
	FCA8H	INSFLG	flag to indicate insert mode 0 = normal mode, otherwise = insert mode
	FCA9H	CSRSW	whether cursor is displayed 0 = no, otherwise = yes ; set by <cursor swicth> of LOCATE statement
	FCAAH	CSTYLE	cursor shape 0 = block, otherwise = underline
	FCABH	CAPST	CAPS key status 0 = CAP OFF, otherwise = CAP ON
	FCACH	KANAST	kana key status 0 = kaka OFF, otherwise = kana ON
	FCADH	KANAMD	kana key arrangement status 0 = 50-sound arrangement, otherwise = JIS arrangement
	FCAEH	FLBMEM	0 when loading BASIC program
	FCAFH	SCRMOD	current screen mode number
	FCB0H	OLDSCR	screen mode reservation area
	FCB1H	CASPRV	character reservation area used by CAS:
	FCB2H	BRDATR	border color code used by PAINT; set by <border color> in PAINT statement
	FCB3H	GXPOS	X-coordinate
	FCB5H	GYPOS	Y-coordinate
	FCB7H	GRPACX	graphic accumulator X-coordinate
	FCB9H	GRPACY	graphic accumulator Y-coordinate
	FCBBH	DRWFLG	flag used in DRAW statement
	FCBCH	DRWSCL	DRAW scaling factor 0 = no scaling, otherwise = scaling
	FCBDH	DRWANG	angle at DRAW
	FCBEH	RUNBNF	flag to indicate BLOAD in progress, BSAVE in progress, or neither
	FCBFH	SAVENT	starting address of BSAVE
	FCC1H	EXPTBL	flag table for expansion slot; whether the slot is expanded
	FCC1H	* EXPTBL	........... whether the basic slot is expanded or not [FCC1H-FCC4H = bit 7= expanded or not
	FCC5H	SLTTBL	current slot selection status for each expansion slot register
	FCC9H	SLTATR	reserves attribute for each slot
	FD09H	SLTWRK	allocates specific work area for each slot
	FD89H	PROCNM	stores name of expanded statement after CALL statement or expansion device after CALL statement or expansion device
	FD99H	DEVICE	used to identify cartridge device
	FD9AH	H.KEYI	MSX Interrupt handler, add a JP to your own here to override the firmwareinterrupts
	FD9FH	H.TIMI	MSXIO timer interrupt handling purpose: adds the timer interrupt handling
	FDA4H	H.CHPH	beginning of MSXIO CHPUT one character output purpose: connects other console device
	FDA9H	H.DSPC	beginning of MSXIO DSPCSR cursor display purpose: connects other console device
	FDAEH	H.ERAC	beginning of MSXIO ERACSR erase cursor purpose: connects other console device
	FDB3H	H.DSPF	beginning of MSXIO DSPFNK function key display purpose: connects other console device
	FDB8H	H.ERAF	beginning of MSXIO ERAFNK erase function key purpose: connects other console device
	FDBDH	H.TOTE	beginning of MSXIO TOTEXT set screen in text mode purpose: connects other console device
	FDC2H	H.CHGE	beginning of MSXIO CHGET get one character purpose: connects other console device
	FDC7H	H.INIP	beginning of MSXIO INIPAT character pattern initialisation purpose: uses other character set
	FDCCH	H.KEYC	beginning of MSXIO KEYCOD key code translation purpose: uses other key arrangement
	FDD1H	H.KYEA	beginning of MSXIO NMI routine Key Easy purpose: uses other key arrangement
	FDD6H	H.NMI	beginning of MSXIO NMI non-maskable interrupt purpose: handles NMI
	FDDBH	H.PINL	beginning of MSXIO PINLIN one line input purpose: uses other console input device or other input method
	FDE0H	H.QINL	beginning of MSXINL QINLIN one line input displaying "?" purpose: uses other console input device or other input method
	FDE5H	H.INLI	beginning of MSXINL INLIN one line input purpose: uses other console input device or other input method
	FDEAH	H.ONGO	beginning of MSXSTS INGOTP ON GOTO purpose: uses other interrupt handling device
	FDEFH	H.DSKO	beginning of MSXSTS DSKO$ disk output purpose: connects disk device
	FDF4H	H.SETS	beginning of MSXSTS SETS set attribute purpose: connects disk device
	FDF9H	H.NAME	beginning of MSXSTS NAME rename purpose: connects disk device
	FDFEH	H.KILL	beginning of MSXSTS KILL delete file purpose: connects disk device
	FE03H	H.IPL	beginning of MSXSTS IPL initial program loading purpose: connects disk device
	FE08H	H.COPY	beginning of MSXSTS COPY file copy purpose: connects disk device
	FE0DH	H.CMD	beginning of MSXSTS CMD expanded command purpose: connects disk device
	FE12H	H.DSKF	beginning of MSXSTS DSKF unusde disk space purpose: connects disk device
	FE17H	H.DSKI	beginning of MSXSTS DSKI disk input purpose: connects disk device
	FE1CH	H.ATTR	beginning of MSXSTS ATTR$ attribute purpose: connects disk device
	FE21H	H.LSET	beginning of MSXSTS LSET left-padded assignment purpose: connects disk device
	FE26H	H.RSET	beginning of MSXSTS RSET right-padded assignment purpose: connects disk device
	FE2BH	H.FIEL	beginning of MSXSTS FIELD field purpose: connects disk device
	FE30H	H.MKI$	beginning of MSXSTS MKI$ create integer purpose: connects disk device
	FE35H	H.MKS$	beginning of MSXSTS MKS$ create single precision real purpose: connects disk device
	FE3AH	H.MKD$	beginning of MSXSTS MKD$ create double precision real purpose: connects disk device
	FE3FH	H.CVI	beginning of MSXSTS CVI convert integer purpose: connects disk device
	FE44H	H.CVS	beginning of MSXSTS CVS convert single precision real purpose: connects disk device
	FE49H	H.CVD	beginning of MSXSTS CVS convert double precision real purpose: connects disk device
	FE4EH	H.GETP	SPDSK GETPTR get file pointer purpose: connects disk device
	FE53H	H.SETF	SPCDSK SETFIL set file pointer purpose: connects disk device
	FE58H	H.NOFO	SPDSK NOFOR OPEN statement without FOR purpose: connects disk device
	FE5DH	H.NULO	SPCDSK NULOPN open unused file purpose: connects disk device
	FE62H	H.NTFL	SPCDSK NTFLO file number is not 0 purpose: connects disk device
	FE67H	H.MERG	SPCDSK MERGE program file merge purpose: connects disk device
	FE6CH	H.SAVE	SPCDSK SAVE save purpose: connects disk device
	FE71H	H.BINS	SPCDSK BINSAV save in binary purpose: connects disk device
	FE76H	H.BINL	SPCDSK BINLOD load in binary purpose: connects disk device
	FD7BH	H.FILE	SPCDSK FILES displey filename purpose: connects disk device
	FE80H	H.DGET	SPCDSK DGET disk GET purpose: connects disk device
	FE85H	H.FILO	SPCDSK FILOU1 file output purpose: connects disk device
	FE8AH	H.INDS	SPCDSK INDSKC disk attribute input purpose: connects disk device
	FE8FH	H.RSLF	SPCDSK; re-select previous drive purpose: connects disk device
	FE94H	H.SAVD	SPCDSK; reserve current disk purpose: connects disk device
	FE99H	H.LOC	SPCDSK LOC function indicate location purpose: connects disk device
	FE9EH	H.LOF	SPCDSK LOC function file length purpose: connects disk device
	FEA3H	H.EOF	SPCDSK EOF function end of file purpose: connects disk device
	FEA8H	H.FPOS	SPCDSK FPOS function file location purpose: connects disk device
	FEADH	H.BAKU	SPCDSK BAKUPT backup purpose: connects disk device
	FEB2H	H.PARD	SPCDEV PARDEV get peripheral name purpose: expands logical device name
	FEB7H	H.NODE	SPCDEV NODEVN no device name purpose: sets default device name to other device
	FEBCH	H.POSD	SPCDEV POSDSK purpose: connects disk device
	FEC1H	H.DEVN	SPCDEV DEVNAM process device name purpose: expands logical device name
	FEC6H	H.GEND	SPCDEV GENDSP FEC6H purpose: expands logical device name
	FECBH	H.RUNC	BIMISC RUNC clear for RUN
	FED0H	H.CLEAR	BIMISC CLEARC clear for CLEAR statement
	FED5H	H.LOPD	BIMISC LOPDFT set loop and default value purpose: uses other default value for variable
	FEDAH	H.STKE	BIMISC STKERR stack error
	FEDFH	H.ISFL	BIMISC ISFLIO file input-output or not
	FEE4H	H.OUTD	meaning: BIO OUTDO execute OUT
	FEE9H	H.CRDO	BIO CRDO execute CRLF
	FEEEH	H.DSKC	BIO DSKCHI input disk attribute
	FEF3H	H.DOGR	GENGRP DOGRPH execute graphic operation
	FEF8H	H.PRGE	BINTRP PRGEND program end
	FEFDH	H.ERRP	BINTRP ERRPTR error display
	FF02H	H.ERRF	BINTRP
	FF07H	H.READ	BINTRP READY
	FF0CH	H.MAIN	BINTRP MAIN
	FF11H	H.DIRD	BINTRP DIRDO execute direct statement
	FF16H	H.FINI	BINTRP
	FF1BH	H.FINE	BINTRP
	FF20H	H.CRUN	BINTRP
	FF20H	H.CRUN	BINTRP
	FF25H	H.CRUS	BINTRP
	FF2AH	H.ISRE	BINTRP
	FF2FH	H.NTFN	BINTRP
	FF34H	H.NOTR	BINTRP
	FF39H	H.SNGF	BINTRP
	FF3EH	H.NEWS	BINTRP
	FF43H	H.GONE	BINTRP
	FF48H	H.CHRG	BINTRP
	FF4DH	H.RETU	BINTRP
	FF52H	H.PRTF	BINTRP
	FF57H	H.COMP	BINTRP
	FF5CH	H.FINP	BINTRP
	FF61H	H.TRMN	BINTRP
	FF66H	H.FRME	BINTRP
	FF6BH	H.NTPL	BINTRP
	FF70H	H.EVAL	BINTRP
	FF75H	H.OKNO	BINTRP
	FF7AH	H.FING	BINTRP
	FF7FH	H.ISMI	BINTRP ISMID$ MID$ or not
	FF84H	H.WIDT	BINTRP WIDTHS WIDTH
	FF89H	H.LIST	BINTRP LIST
	FF8EH	H.BUFL	BINTRP BUFLIN buffer line
	FF93H	H.FRQI	BINTRP FRQINT
	FF98H	H.SCNE	BINTRP
	FF9DH	H.FRET	BINTRP FRETMP
	FFA2H	H.PTRG	BIPTRG PTRGET get pointer purpose: uses variable other than default value
	FFA7H	H.PHYD	MSXIO PHYDIO physical disk input-output purpose: connects disk device
	FFACH	H.FORM	MSXIO FORMAT format disk purpose: connects disk device
	FFB1H	H.ERRO	BINTRP ERROR purpose: error handling for application program
	FFB6H	H.LPTO	MSXIO LPTOUT printer output purpose: uses printer other than default value
	FFBBH	H.LPTS	MSXIO LPTSTT printer status purpose: uses printer other than default value
	FFC0H	H.SCRE	MSXSTS SCREEN statement entry purpose: expands SCREEN statement
	FFC5H	H.PLAY	MSXSTS PLAY statement entry purpose: expands PLAY statement
	FFCAH	FCALL	hook used by expanded BIOS
	FFCFH	DISINT	used by DOS
	FFD4H	ENAINT	used by DOS

Cartridge Header

Address	Bytes	Purpose	Detail	Sample
&0000	2	ID	Fixed	AB
&0002	2	INIT	Start Address	&4010
&0004	2	STATEMENT	Call address	&0000
&0006	2	DEVICE	Dev address	&0000
&0008	2	TEXT	Basic Address	&0000
&0010		Program Code�

Disk File Header

Position	Bytes	Content	Details	Example
&0000	1	&FE	Magic Number	&FE
&0001	2	Load address	Address to load into memory	&810A
&0003	2	End Address	Last address in memory (Load address+Size)	&910A
&0005	2	Execute Address	Address to call program	&810A
&0007	Program Code

MSX and MSX2 Programming Tutorials:

Lesson P5 - Bitmap graphics on the TI-83 and MSX
Lesson P7 - Keyreading on the MSX, Enterprise and TI-83
Lesson P10 - Tilemap graphics on the MSX1
Lesson P11 - Tilemap graphics on the MSX2

General Z80 Assembly Tutorials:
B. Beginner series - Learn the basics
A. Advanced series - In more detail
M. Multiplatform series - programming methods that work on all systems

MSX and MSX2 Links:

OpenMSX - The best MSX emulator - you'll need to find your own roms for disk system emulaton (For disk images I reccomend emulating the hb-f1xdj)
Grauw.nl - great resources and samplecode for MSX development
MSX2 Technical Handbook - full breakdown of the MSX2 hardware - all the info you will need for development purposes
Basic Manual - You'll want to know at least enough basic to do calls and operate the computer
V9938 Programmer?s Guide - Detailed manual on programming the MSX2 V9938 GPU
MSX.Org - Web community full of helpful people!