memory.lst

A Programmer s Reference to BIOS, DOS, and Third-Party Calls

Size:	BYTE
Note:	cleared to 00h at start of disk operation, set to FFh by IRQ14
	  handler when hard disk controller completes command
SeeAlso: MEM 0040h:008Ch,MEM 0040h:008Dh,MEM 0040h:008Fh
--------B-M0040008F--------------------------
MEM 0040h:008Fh U - DISKETTE CONTROLLER INFORMATION [not XT]
Size:	BYTE
SeeAlso: MEM 0040h:008Ch,MEM 0040h:008Dh,MEM 0040h:008Eh

Bitfields for diskette controller information:
Bit(s)	Description	(Table M0029)
 7	reserved
 6	=1 drive 1 determined
 5	=1 drive 1 is multi-rate, valid if drive determined
 4	=1 drive 1 supports 80 tracks, always valid
 3	reserved
 2	=1 drive 0 determined
 1	=1 drive 0 is multi-rate, valid if drive determined
 0	=1 drive 0 supports 80 tracks, always valid
Note:	EHD BIOS sets this byte to 01h and never alters it again
--------B-M00400090--------------------------
MEM 0040h:0090h - DISKETTE DRIVE 0 MEDIA STATE
Size:	BYTE
SeeAlso: MEM 0040h:0091h

Bitfields for diskette drive media state:
Bit(s)	Description	(Table M0030)
 7-6	data rate
	00=500kbps, 01=300kbps, 10=250kbps, 11=1Mbps
 5	double stepping required (e.g. 360kB in 1.2MB)
 4	media type established
 3	drive capable of supporting 4MB media
 2-0	on exit from BIOS, contains
	000 trying 360kB in 360kB
	001 trying 360kB in 1.2MB
	010 trying 1.2MB in 1.2MB
	011 360kB in 360kB established
	100 360kB in 1.2MB established
	101 1.2MB in 1.2MB established
	110 reserved
	111 all other formats/drives
SeeAlso: #M0031,#M0032
--------B-M00400091--------------------------
MEM 0040h:0091h - DISKETTE DRIVE 1 MEDIA STATE
Size:	BYTE
SeeAlso: MEM 0040h:0090h,#M0030
--------B-M00400092--------------------------
MEM 0040h:0092h U - DISKETTE DRIVE 0 MEDIA STATE AT START OF OPERATION
Size:	BYTE
Note:	officially "Drive 2 media state"
SeeAlso: MEM 0040h:0093h"DRIVE 1"

Bitfields for diskette drive 0 media state at start of operation:
Bit(s)	Description	(Table M0031)
 7-3 (see #M0030)
 2	multiple data rate capability determined
 1	multiple data rate capability
 0	=1 if drive has 80 tracks, =0 if 40 tracks
SeeAlso: #M0030,#M0032
--------d-M00400092--------------------------
MEM 0040h:0092h - Olivetti Quaderno - HARD DISK POWERDOWN COUNTDOWN CLOCK TICKS
Size:	BYTE
Note:	hard disk is turned off when counter reaches zero
--------B-M00400093--------------------------
MEM 0040h:0093h U - DISKETTE DRIVE 1 MEDIA STATE AT START OF OPERATION
Size:	BYTE
Note:	officially "Drive 3 media state"
SeeAlso: MEM 0040h:0092h"DRIVE 0"

Bitfields for diskette drive 1 media state at start of operation:
Bit(s)	Description	(Table M0032)
 7-3	(see #M0030)
 2	multiple data rate capability determined
 1	multiple data rate capability
 0	=1 if drive has 80 tracks, =0 if 40 tracks
--HP 100LX/200LX--
	display control status
 0	=1 if DISPCTL -K
 1	=1 if DISPCTL -C
--------B-M00400094--------------------------
MEM 0040h:0094h - DISKETTE DRIVE 0 CURRENT TRACK NUMBER
Size:	BYTE
SeeAlso: MEM 0040h:0095h
--------B-M00400095--------------------------
MEM 0040h:0095h - DISKETTE DRIVE 1 CURRENT TRACK NUMBER
Size:	BYTE
SeeAlso: MEM 0040h:0094h
--------K-M00400096--------------------------
MEM 0040h:0096h - KEYBOARD STATUS BYTE 1
Size:	BYTE
SeeAlso: MEM 0040h:0097h,INT 16/AH=11h

Bitfields for keyboard status byte 1:
Bit(s)	Description	(Table M0033)
 7	=1 read-ID in progress
 6	=1 last code read was first of two ID codes
 5	=1 force Num Lock if read-ID and enhanced keyboard
 4	=1 enhanced keyboard installed
 3	=1 Right Alt pressed
 2	=1 Right Ctrl pressed
 1	=1 last code read was E0h
 0	=1 last code read was E1h
SeeAlso: #M0034,#M0010
--------K-M00400097--------------------------
MEM 0040h:0097h - KEYBOARD STATUS BYTE 2
Size:	BYTE
SeeAlso: MEM 0040h:0096h,INT 16/AH=11h

Bitfields for keyboard status byte 2:
Bit(s)	Description	(Table M0034)
 7	=1 keyboard transmit error flag
 6	=1 LED update in progress
 5	=1 RESEND received from keyboard
 4	=1 ACK received from keyboard
 3	reserved, must be zero
 2	Caps Lock LED
 1	Num Lock LED
 0	Scroll Lock LED
SeeAlso: #M0033,#M0010
--------B-M00400098--------------------------
MEM 0040h:0098h - TIMER2 (AT, PS exc Mod 30) - PTR TO USER WAIT-COMPLETE FLAG
Size:	DWORD
Note:	(see INT 15/AX=8300h)
SeeAlso: MEM 0040h:009Ch,INT 15/AH=83h,INT 15/AH=86h
--------B-M0040009C--------------------------
MEM 0040h:009Ch - TIMER2 (AT, PS exc Mod 30) - USER WAIT COUNT IN MICROSECONDS
Size:	DWORD
SeeAlso: MEM 0040h:0098h,MEM 0040h:00A0h,INT 15/AH=83h,INT 15/AH=86h
--------V-M0040009F--------------------------
MEM 0040h:009Fh - HP 100LX/200LX - VIDEO ZOOM MODE
Size:	BYTE

(Table M0035)
Values for HP 100LX/200LX video zoom mode:
 02h	80x25 mono
 03h	80x25 color
 80h	64x18 mono
 81h	64x18 color
 82h	40x25 mono
 83h	40x25 color
 84h	40x16 mono
 85h	40x16 color
SeeAlso: INT 10/AH=D0h
--------B-M004000A0--------------------------
MEM 0040h:00A0h - TIMER2 (AT, PS exc Mod 30) - WAIT ACTIVE FLAG
Size:	BYTE
SeeAlso: MEM 0040h:009Ch,INT 15/AH=83h,INT 15/AH=86h

Bitfields for Timer2 wait active flag:
Bit(s)	Description	(Table M0036)
 7	wait time elapsed
 6-1	reserved
 0	INT 15/AH=86h has occurred
--------N-M004000A1--------------------------
MEM 0040h:00A1h - BIT 5 SET IF LAN SUPPORT PROGRAM INTERRUPT ARBITRATOR PRESENT
Size:	BYTE
Note:	DEVICE=DXMA0MOD.SYS
--------N-M004000A2--------------------------
MEM 0040h:00A2h - RESERVED FOR NETWORK ADAPTERS
Size:	6 BYTEs
--------d-M004000A4--------------------------
MEM 0040h:00A4h - PS/2 Mod 30 - SAVED FIXED DISK INTERRUPT VECTOR 
Size:	DWORD
--------V-M004000A8--------------------------
MEM 0040h:00A8h - VIDEO (EGA/MCGA/VGA) - POINTER TO VIDEO SAVE POINTER TABLE
Size:	DWORD
SeeAlso: INT 10/AH=1Ch

Format of Video Save Pointer Table [EGA/VGA/MCGA only]:
Offset	Size	Description	(Table M0037)
 00h	DWORD	ptr to Video Parameter Table
 04h	DWORD	ptr to Parameter Dynamic Save Area, else 0 [EGA/VGA only]
 08h	DWORD	ptr to Alphanumeric Character Set Override, else 0
 0Ch	DWORD	ptr to Graphics Character Set Override, else 0
 10h	DWORD	[VGA only] ptr to Secondary Save Pointer Table, must be valid
 14h	DWORD	reserved, zero
 18h	DWORD	reserved, zero
Note: table initially in ROM, copy to RAM to alter, then update 40h:A8h.
 
Format of Secondary Video Save Pointer Table [VGA only]:
Offset	Size	Description	(Table M0038)
 00h	WORD	Length of this table in bytes, including this word (1Ah)
 02h	DWORD	ptr to Display Combination Code Table, must be valid
 06h	DWORD	ptr to second Alphanumeric Character Set Override, else 0
 0Ah	DWORD	ptr to User Palette Profile Table, else 0
 0Eh	DWORD	reserved, zero
 12h	DWORD	reserved, zero
 16h	DWORD	reserved, zero
Note: table initially in ROM, copy to RAM to alter, then alter Save Ptr Table.
 
Format of Display Combination Code Table [VGA only]:
Offset	Size	Description	(Table M0039)
 00h	BYTE	Number of entries in the DCC table at offset 04h
 01h	BYTE	Version number
 02h	BYTE	Maximum display type code that can appear in DCC table
 03h	BYTE	reserved
 04h 2N BYTEs	Each pair of bytes gives a valid display combination, one
		  display type per byte (see #M0040)

(Table M0040)
Values for Display Combination display type:
 00h	 no display
 01h	 MDA with mono display
 02h	 CGA with color display
 03h	 reserved
 04h	 EGA with color display
 05h	 EGA with mono display
 06h	 Professional Graphics Controller
 07h	 VGA with mono display
 08h	 VGA with color display
 09h	 reserved
 0Ah	 MCGA with digital color display
 0Bh	 MCGA with analog mono display
 0Ch	 MCGA with analog color display
 FFh	 unrecognised video system
SeeAlso: #M0039
 
Format of Video Parameter Table [EGA, VGA only]:
Offset	Size	Description	(Table M0041)
 00h-03h	Modes 00h-03h in 200-line CGA emulation mode
 04h-0Eh	Modes 04h-0Eh
 0Fh-10h	Modes 0Fh-10h when only 64kB RAM on adapter
 11h-12h	Modes 0Fh-10h when >64kB RAM on adapter
 13h-16h	Modes 00h-03h in 350-line mode
 17h		VGA Modes 00h or 01h in 400-line mode
 18h		VGA Modes 02h or 03h in 400-line mode
 19h		VGA Mode  07h in 400-line mode
 1Ah-1Ch	VGA Modes 11h-13h
Note:	An array of 23 [EGA] or 29 [VGA] elements, each element being 64
	  bytes long.  Elements appear in the above order.
 
Format of Video Parameter Table element [EGA, VGA only]:
Offset	Size	Description	(Table M0042)
 00h	BYTE	Columns on screen		  (see 40h:4Ah)
 01h	BYTE	Rows on screen minus one	  (see 40h:84h)
 02h	BYTE	Height of character in scan lines (see 40h:85h)
 03h	WORD	Size of video buffer		  (see 40h:4Ch)
 05h  4 BYTEs	Values for Sequencer Registers 1-4
 09h	BYTE	Value for Miscellaneous Output Register
 0Ah 25 BYTEs	Values for CRTC Registers 00h-18h
 23h 20 BYTEs	Values for Attribute Controller Registers 00h-13h
 37h  9 BYTEs	Values for Graphics Controller Registers 00h-08h
 
Format of Video Parameter Table [MCGA only] {guesswork from inspection}:
Offset	Size	Description	(Table M0043)
    - 16 triplet BYTEs of R,G,B DAC info for 16 colors;
    - An array of 11 elements, each element being 32 bytes long.
	  Elements appear in the order:
		Modes 00h,01h in 200-line mode for digital displays
		Modes 00h,01h in 400-line mode for analog displays
		Modes 02h,03h in 200-line mode for digital displays
		Modes 02h,03h in 400-line mode for analog displays
		Modes 04h,05h in 200-line mode for digital displays
		Modes 04h,05h in 400-line mode for analog displays
		Mode  06h in 200-line mode for digital displays
		Mode  06h in 400-line mode for analog displays
		Mode  11h
		Mode  13h in 200-line mode for digital displays
		Mode  13h in 400-line mode for analog displays
 
Format of Video Parameter Table element [MCGA only]:
Offset	Size	Description	(Table M0044)
 00h	BYTE	Columns on screen		  (see 40h:4Ah)
 01h	BYTE	Rows on screen minus one	  (see 40h:84h)
 02h	BYTE	Height of character in scan lines (see 40h:85h)
 03h	WORD	Size of video buffer		  (see 40h:4Ch)
 05h	WORD	??? always zero
 07h 21 BYTEs	Video data registers 00h-14h to port 3D5h indexed by 3D4h
 1Ch	BYTE	PEL Mask to port 3C6h
 1Dh	BYTE	CGA Mode Control to port 3D8h
 1Eh	BYTE	CGA Border Control to port 3D9h
 1Fh	BYTE	Extended Mode Control to port 3DDh
 
Format of Video Parameter Dynamic Save Area [EGA, VGA only]:
Offset	Size	Description	(Table M0045)
 00h 16 BYTEs	Last data written to Attribute Contr. Palette Registers 0-15
 10h	BYTE	Last data written to Attribute Controller Overscan Register
 11h-FFh	Reserved
		Note: Need for table was that EGA registers were write-only.
		Note: If default values (from the Video Parameter Table) are
		      over-ridden at a mode set by the VGA User Palette Profile
		      Table, then the Dynamic Save Area is updated with the
		      default values, not the User Profile ones.
 
Format of Alphanumeric Character Set Override:
Offset	Size	Description	(Table M0046)
 00h	BYTE	Length in bytes of each character in font table
 01h	BYTE	Character generator RAM bank to load, 0=normal
 02h	WORD	Number of characters in font table, normally 256
 04h	WORD	Code of first character in font table, normally 0
 06h	DWORD	ptr to font table
 0Ah	BYTE	Displayable rows (FFh=use maximum calculated value)
 0Bh	BYTEs	Array of mode values to which this font is to pertain
	BYTE	FFh end of array
 
Format of Second Alphanumeric Character Set Override:
Offset	Size	Description	(Table M0047)
 00h	BYTE	Length in bytes of each character in font table
 01h	BYTE	Character generator RAM bank to load, normally non-zero
 02h	BYTE	reserved
 03h	DWORD	ptr to font table
 07h	BYTEs	Array of mode values to which this font is to pertain
	BYTE	FFh end of array
Note:	Authorities differ, some say same as first override above, but IBM
	  says it is as shown above
 
Format of Graphics Character Set Override:
Offset	Size	Description	(Table M0048)
 00h	BYTE	Number of displayable character rows
 01h	WORD	Length in bytes of each character in font table
 03h	DWORD	ptr to font table
 07h	BYTEs	Array of mode values to which this font is to pertain
	BYTE	FFh end of array
 
Format of User Palette Profile Table [VGA only]:
Offset	Size	Description	(Table M0049)
 00h	BYTE	Underlining: 01h=enable in all alphanumeric modes
			     00h=enable in monochrome alphanumeric modes only
			     FFh=disable in all alphanumeric modes
 01h	BYTE	reserved
 02h	WORD	reserved
 04h	WORD	Number (0-17) of Attribute Controller registers in table
 06h	WORD	Index (0-16) of first Attribute Controller register in table
 08h	DWORD	ptr to table of Attribute Controller registers to override
			Table is an array of BYTEs.
 0Ch	WORD	Number (0-256) of video DAC Color registers in table