MSX1:

• The Main-ROM is placed on the memory pages 0000h~3FFFh and 4000h~7FFFh.
• The routine looks for the RAM in the Primary Slots from 0 to 3 on the memory pages 8000h~BFFF and C000h~FFFFh. If a Primary Slot is expanded, it looks in Secondary Slots from 0 to 3 before moving on to the next Primary Slot. Thus the routine selects the first RAM that it finds on each page without taking into account the Memory Mapper.
• Initializes the work area, variables and Hooks.
• Look for a possible Rom in the primary Slots from 0 to 3 on the memory pages 4000h~7FFF and 8000h~BFFFh to execute it. (When a Rom is found on the page 4000h~7FFFh, the 8000h~BFFFh page will contain main RAM if the MSX has 32kB or higher. When a Rom is found on the page 8000h~BFFFh, the page 4000h~7FFFh will contain the Main-ROM).
• Replace the Main-ROM on the page 4000h~7FFFh and start the Basic.

MSX2:

• Proceed in the same way as the MSX1 except that the Memory Mapper registers are initialized as described in the page on the Memory Mapper.

MSX2+:

• Same as MSX2 except that the routine takes into account whether it is about starting the computer or rebooting. In the second case, the MSX logo will not be displayed. (Bit 5 of I/O port F4h is used for this.)

MSX Turbo R:

• Same as MSX2+ except that the internal RAM will be automatically selected as main Ram in R800 mode because the internal RAM is clocked at 7.159 MHz instead of 3.5795 for the extensions.

Example:

	ld	hl,LETTER
	rst	08h
	db	"A"
	rst	08h
	db	"B"
	ret
LETTER: db	"AB"

• This routine disables the interrupts.
• This routine also exists under MSX-DOS.

• This routine skips the spacing codes (020h).
• Call the hook H.CHRG (0FF48h).

• This routine disables the interrupts.
• Call the hook H.OUTD (0FEE4h).
• This routine also exists under MSX-DOS.

• Interrupts are disabled by the routine.
• Can not call another extended slot of the same primary slot where the BIOS is located.
• This routine also exists under MSX-DOS.

• Unlike the RDSLT, WRSLT and CALSLT routines, the primary slot switching is performed directly in page 0 (0000H to 3FFFh), thus, addresses in page 0 will cause a system crash.
• This routine also exists under MSX-DOS, where it will work also for page 0, with the sole limit that it cannot call another extended slot of the same primary slot where the BIOS is located.
• This routine disables the interrupts.

; Back to Basic from MSX-DOS 

MNROM	equ	0FCC1h
ENASLT 	equ	00024h
RETURN	equ	0409Bh

	org	0D000h
DEBUT:
	ld	a,(MNROM)
	ld	h,0
	call	ENASLT	; Select main ROM on page 0000H~3FFFh
	ld	a,(MNROM)
	ld	h,040h
	call	ENASLT	; Select main ROM on page 4000H~7FFFh
	jp	RETURN	; 

integer type			single precision real type
   C = 1				C = 1
   S = 1 *				S = 0
   Z = 0				Z = 0
   P/V = 1				P/V = 0 *
   
string type			double precision real type
   C = 1				C = 0 *
   S = 0				S = 0
   Z = 1 *				Z = 0
   P/V = 1				P/V = 1
Types can be recognised by the flag marked by "*".

	RST	30H
	DB	n	;n is the slot number (same as RDSLT)
	DW	nn	;nn is the called address

• Interrupts are disabled by the routine.
• Can not call another extended slot of the same primary slot where the BIOS is located.
• This routine also exists under MSX-DOS.

• This routine is called at each interruption.
• Calls Hooks H.KEYI (0FD9Ah) and H.TIMI (0FD9Fh).
• Sub-ROM call for Roma-Kana conversions on Japanese MSX2 or later.

;Read 4 bytes from VRAM

VDP.DR	equ	0006h

	ld	hl,0		;VRAM address
	call	SETWRT

	ld	hl,DATA
	ld	b,7		;Text length
	ld	a,(VDP.DR)	;Data read port
	ld	c,a
LOOP:
	ini			;You can replace this two
	jr	nz,LOOP		;lines with inir on MSX2/2+/turbo R
	ret
DATA:
	db	0,0,0,0		;Data read from VRAM are stored here

;Print "Hello!" at the top left of the screen (SCREEN1)

VDP.DW	equ	0007h

	ld	hl,(T32NAM)	;Characters table address in SCREEN1
	call	SETWRT

	ld	hl,TXT
	ld	b,7		;Text length
	ld	a,(VDP.DW)	;Data write port
	ld	c,a
HELLO:
	outi			;You can replace this two
	jr	nz,HELLO	;lines with otir on MSX2/2+/turbo R
	ret
TXT:
	db	"Hello!"

• Interrupts must be disabled to call this routine.
• After initialization, the registers will have the following values.

R#0 = 01010101	R#1 = 00000000	 R#2 = 00000000
R#3 = 00000000	R#4 = 00000000	 R#5 = 00000000
R#6 = 00000000	R#7 = 10111000	 R#8 = 00000000
R#9 = 00000000	R#10 = 00000000	 R#11 = 00001011
R#12 = 00000000	R#13 = 00000000

• See page on PSG for more details on the registers.
• The interrupts are disabled then enabled again by the routine.

• See page on PSG for more details on the registers.
• The interrupts are not disabled by the routine.

• Calls the hook H.CHGE (0FDC2h).
• The variables SCNCNT (0F3F7h) and REPCNT (0F3F7h) are used to set the scanning intervals of the keyboard.

• Calls the hook H.LPTO (0FFB6h).
• CTRL+STOP allows you to exit the routine if there is a problem with the printer.

• GRPHED (0FCA6h) is taken into account to indicate whether it is an extended graphic character (between 65 and 95) or not.
• See MSX font for detail on extended graphic characters.

• End of line is indicated by the code 00h
• Calls to Hook H.PINL (0FDDBh).
• If AUTFLG (0F6AAh) is set, calls the routine INLIN (000B1h) instead.

• Calls to Hook H.INLI (0FDE5h).
• Compared to PINLIN, this routine takes into account that the characters placed behind cursor. The prompt is usable.

• Call the Hook H.DSPF (0FDB3h)
• Call the routine DSPFNK (000CFh in Main-ROM) to display the text of the function keys

• Call the Hook H.TOTE (0FDBDh)
• This routine calls CHGMDP (001B5h in Sub-ROM) on MSX2 or later

x 0 x 0 0 0 0 0
|   |
|   1 if the system has already initialized. (MSX turbo R)
|
This bit is reset when a hard reset is performed then set
during the hard reset.    

x 0 x 0 0 0 0 0
|   |
|   Remains set until a hard reset. (MSX turbo R)
|
This bit is reset when a hard reset is performed then set
during the hard reset. Must not be changed by the user.

 LED 0 0 0 0 0 x x
  |            0 0 = Z80 mode (with ROM)
  |            0 1 = R800 mode with ROM
  +----------- 1 0 = R800 mode with RAM

• LED indicates whether the Turbo LED is switched with the CPU.
• The system Roms (Main-ROM, Sub-ROM and Kanji Driver ROM) are replaced by their copy in RAM keeping the same slots in R800 mode with RAM write-protected. This mode speeds up the execution of programs, but it loses the last four pages of the Memory Mapper to the user.
• The CPU can be switched at any time from Z80A to R800 mode with ROM and vice versa. However, the switch to R800 mode with RAM must be done preferably at the start of the MSX only.
• Using the R800 under MSX-DOS1 can damage the files being manipulated.

 v 0 0 0 0 0 x x
 |           | |
 |           +-+-- Quality parameter (00 = 15,75kHz ;
 |                 01 =7,875kHz ; 10 = 5,25kHz et 11 = 3,9375kHz)
 +---------------- VRAM usage flag

BC = Length of area to play
E = Most signifiant 3 bits of the address when using VRAM
HL= Start address in RAM or VRAM

• This routine always uses the R800. If the Z80A is used when calling this routine, the R800 mode with ROM will be used and will then replace the Z80A before give bak hand.
• Interruptions are disabled while this routine is running.

 v t t t t c x x
 | | | | | | | |
 | | | | | | +-+-- Quality parameter (00 = 15,75kHz ;
 | | | | | |       01 =7,875kHz ; 10 = 5,25kHz et 11 = 3,9375kHz)
 | | | | | +------ Zero-data compression
 | +-+-+-+-------- Treshold
 +---------------- VRAM usage flag
 

BC = Length of area to play
D = Bit 0 = Bit 17 of area length when using VRAM
E = Bit 0 = Bit 17 os start address when using VRAM
HL = Start address in RAM or VRAM

• This routine always uses the R800. If the Z80A is used when calling this routine, the R800 mode with ROM will be used and will then replace the Z80A before give bak hand.
• Interruptions are disabled while this routine is running.
• Recording at 15.75kHz in R800 mode with ROM causes an error (CY is reset).
• Press the STOP key to interrupt a recording.