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MSX BIOS Entry List

Slot ID (or slot address) is MSX-BIOS way to represent the slot and sub-slot location in a byte. The byte contains following info:

an example to interpret this from pascal is as follows:

procedure slotID(nValue:byte);
(** nValue is for example mem[$F344] **)
var
    num,num2: byte;
    exp : boolean;
begin;
        num:=nValue;
        num:= (num shl 6);
        num:= (num shr 6);
        if ((nValue and 128) = 128) then exp:=True else exp:=false;
        num2:=nValue;
        num2:=(num2 shl 4);
        num2:=(num2 shr 6);
        writeln('Slot-ID',num);
        writeln('subslot:',num2);
        writeln('expanded:',exp);
end;

Slot ID

MSX SUBROM Entry List

MSX 2 SUBROM BIOS Entries

Physical input/output for disk devices (See PHYDIO in main BIOS)

Input:

• F = Carry set for write, carry reset for read
• A = Drive number (0=A:)
• B = Number of sectors to read/write
• C = Media descriptor
  • F8h for 360K floppy disk, 3,5 inch, sigle-side, 9 sector
  • F9h for 720K floppy disk, 3,5 inch, double-side, 9 sector
  • FAh for 320K floppy disk, 3,5 inch, sigle-side, 8 sector
  • FBh for 640K floppy disk, 3,5 inch, double-side, 8 sector
  • FCh for 180K floppy disk, 5,25 inch, sigle-side, 9 sector
  • FDh for 360K floppy disk, 5,25 inch, double-side, 9 sector
  • FEh for 160K floppy disk, 5,25 inch, sigle-side, 8 sector
  • FFh for 320K floppy disk, 5,25 inch, double-side, 8 sector
• DE = Logical sector number (starts at 0)
• HL = Transfer address

Output:

• F = Carry set on error, carry reset on success
• A = If error: errorcode
• B = Number of sectors transferred (always)

Error codes can be:

Check if disk has been changed.

Input:

• A = Drive number (0=A:)
• B = Media descriptor
• C = Media descriptor
• HL = Base address of DPB

Output:

• F = Carry set on error, carry reset on success
• A = If error: errorcode (see DSKIO)
• B = if success: 1=Disk not changed, 0=Unknown, -1=Disk changed

Note: If the disk has been changed or may have been changed (unknown) read the boot sector or the FAT sector for a disk media descriptor and transfer a new DPB as with GETDPB

Get Drive Parameter Block

Input:

• A = Drive number
• B = First byte of FAT (media descriptor)
• C = Media descriptor
• HL = Base address of DPB

Output: HL+1 … HL+18 = DPB for specified drive

Note: DPB consists of

Get string that describes disk formatting options.

Input: None

Output: HL = Address of zero terminated character string (ASCIIZ) with the text with choices for a DSKFMT If there is no choice (only 1 format supported) return HL = 0

Format disk

Input:

• A = Choice specified by user (1-9). See CHOICE
• D = Drive number (0=A:)
• HL = Begin address of work area
• BC = Length of work area

Output:

• F = Carry flag reset on success, carry flag set on error
• A = If error: errorcode

Error codes can be:

Notes: Also writes a MSX boot sector at sector 0, clears all FATs (media descriptor at first byte, 0FFh at second/third byte and rest zero) and clears the directory (filling it with zeros)

Stop the drive motor of the corresponding interface.

Input: None

Output: None

Modify: AF, BC, DE, HL, IX et IY.

Notes: Not all diskinterfaces support this entry. Only valid when 401FH <> 00H

BASIC cold start. Start the Basic environment and eventually run a file of Basic program from a program in machine language.

Set the variable REBOOT (0F340h) to 0 to run the AUTOEXEC.BAS file (at the root of the disk). Otherwise, there will be a return to Basic. Under MSX-DOS, when the REBOOT variable (0F340h) contains a value other than 0 it is possible to run another Basic program whose file name and length is specified in DTA (0080h).

Input: None

Output: None (Does not return)

Examples:

1. ; Quit your DOS program and launch a BASIC program saved as NAME.BAS
    
   CALSLT	equ	001Ch
   DTA	equ	0080h
   BASENT	equ	04022h
   REBOOT	equ	0F340h
   MASTER	equ	0F348h
    
   	org	0100h
    
   	ld	a,1	; Not 0 to ignore the AUTOEXEC.BAS if present
   	ld	(REBOOT),a
    
   	ld	hl,NAME
   	ld	de,DTA
   	ld	bc,END-NAME
   	ldir		; Copy the file name
    
   	ld	ix,BASENT
   	ld	iy,(MASTER-1)	; Slot of the Master Disk-ROM
   	jp	CALSLT
   NAME:
   	db	END-NAME	; Length
   	db	"NAME.BAS",0
   END:

2. ; Quit your DOS program and go to BASIC
    
   CALSLT	equ	001Ch
   DTA	equ	0080h
   BASENT	equ	04022h
   REBOOT	equ	0F340h
   TEMPST	equ	0F67Ah
   MASTER	equ	0F348h
    
   	org	0100h
    
   	ld	a,1	; Not 0 to ignore the AUTOEXEC.BAS if present
   	ld	(REBOOT),a
    
   	ld	a,0
   	ld	(DTA),a	; No file name
    
   	ld	ix,(TEMPST)	; Erases 3 bytes
   	ld	(ix),0	; from the
   	ld	(ix+1),0	; area reserved for
   	ld	(ix+2),0	; the BASIC program
    
   	ld	ix,BASENT
   	ld	iy,(MASTER-1)	; Slot of the Master Disk-ROM
   	jp	CALSLT

3. ; Quit your DOS program and launch the AUTOEXEC.BAS under BASIC
    
   CALSLT	equ	001Ch
   BASENT	equ	04022h
   REBOOT	equ	0F340h
   TEMPST	equ	0F67Ah
   MASTER	equ	0F348h
    
   	org	0100h
    
   	ld	a,0	; 0 to run the AUTOEXEC.BAS file
   	ld	(REBOOT),a
    
   	ld	ix,(TEMPST)	; Erases 3 bytes
   	ld	(ix),0	; from the
   	ld	(ix+1),0	; area reserved for
   	ld	(ix+2),0	; the BASIC program
    
   	ld	ix,BASENT
   	ld	iy,(MASTER-1)	; Slot of the Master Disk-ROM
   	jp	CALSLT

4. ENASLT equ 0024H
   MASTER equ 0F348H
   BASENT equ 04022H
    
          LD A,(MASTER)
          LD H,40H
          CALL ENASLT
          JP BASENT

Format a disk in BASIC by asking the user for settings.

This routine sets the Carry flag to 1 and then calls the FORMTK (04026h) routine below.

Input: None

Output: None

Note: This is interactive process with user (prompts for drive and format choice)

Format a disk from a program with user-specified parameters.

Input:

• F = Reset the Carry flag
• HL = Start of buffer
• BC = Size of buffer

Output: None

Stop all drives of all controllers

Input: None

Output: None

Modify: AF, BC, DE, HL, IX et IY.

Note: This routine only exists if the interface manages removable disks. Otherwise, 04029h will contain the zero byte (00h). Some HDD interfaces have wrongly implemented this as a HDD powerdown (HSH/MAK)

Get Slot ID of disk ROM

Input: None

Output: A = Slot ID

Get MSX-DOS system bottom

Input: None

Output: HL = Lowest address used by the base MSX-DOS system

Disk-ROM BIOS

Some workspace in MSX work area

MSX BIOS calls

Main-ROM BIOS

Calling the BIOS from MSX-DOS