PS2 and PC BIOS Interface Technical Reference Apr87

8/13/2019 PS2 and PC BIOS Interface Technical Reference Apr87

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Preface

This technical reference provid


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Section 2 Interrupts, cinterrupts function across tPersonal Computer producare noted.

Section 3 BIOS Data Arinformation about regular


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Contents BIOS

Section 1. Introduction to B


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Adapter ROMVideo Function Compatibili ty

. Video Presence Test Video Mode Switching

Multitasking Provisions System Identification Application Guidelines


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Figures BIOS

2-1. Interrupts


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3-25. Fixed Disk Drive ParProducts Except Mod

3-26. Fixed Disk Drive DriBIOS Dated 11/10/82

3-27. Fixed Disk Drive ParDated 11/10/82)

3 28 Fixed Disk Drive Par


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Section 1. Introduction to

Interrupts


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Notes:


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The Basic Input/Output SystemPersonal Computer products isisolates operating systems andhardware devices. BIOS routiprogrammers to perform blockconcern for device addressesThe BIOS also provides system


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To read the time, the following

OV AH 0INT l H

;Function s

;Read the time

The BIOS interrupt handlers savand those registers that return a


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To determine the BIOS versioprogram. The date that is dispfor that system:

10 DEF SEG= HF00020 FOR X= HFFF5 TO HFFFC30 PRINT CHR (PEEK(X;


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Notes:


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Section 2 nterrup

Interrupt 02H - Nonmaskable


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Notes


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The following figure lists eachapplicable, the location of a m

InterruptNumber (Hex)

1

Interrupt Fun

Divide by 0Single Step


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Interrupt 02H - Nonmask

For PCjr the nonmaskable ininterrupt.


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For PC Convertible, the NMI the real-time clock, and the syactivated upon the I/O channel

Notes:

1 An 8087 math coprocesso


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Interrupt 05H Print Scr

This interrupt handler prints issued the cursor position isof the interrupt INT 05H run


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Interrupt 08H System

This interrupt handler contthe system timer. The input fis 65536 resulting in approxim


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Interrupt 09H Keyboard

This interrupt h ndler is issukeystroke.


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For AT BIOS dated 6/10/85 andConvertible, and Personal SysKeyboard Intercept), is issued

60H. This allows the system tof Interrupt EOI) processing i


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Interrupt 10H Video

The following is a summary

AH) = OOH - Set Mode


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AH) = OOH - Set Mode

AL) Requested

The fol lowing table describes


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Mode Display BoxHex) Size Size Supporting I

2 3 640x200 8x8 PCjr CGA640x200 8x8 EGA, and P

Except Mo

640x350 8x14 EGA and P


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Notes:

1 P jr and IBM Color/Gra

a. The cursor is not dib. Modes 0 2 and 5 a

color burst is not ena


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4. Personal System 2 Mod

a. The cursor is not dispb. Modes 0, 2, and 5 arc. The power-on default d. During mode set, if bi

cleared.


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Notes:

1. The BIOS maintains o

2. For Personal Systemhardware video ports,multiplied by 2 and in


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AH) OS - Select Acti

For PCjr

AL) = 80H - Readpage


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AH) = 08H - Read AHri

BH) - Page numbermaximum pag

On Return:AL) - CharacterAH) Att ib t


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AH) = OAH - Write Cha

BH) - Page number

maximum pagCX) - Count of chAL) - Character to


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For graphics modes suppo

BH) - Page numbermaximum pag

AH) O H - Read Dot


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AH) 10H - Set Palette R

For PCjr systems with EGproducts except Model

Al) = 00H Set iBl) PaletteBH) V l


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Al) = 10H - Set iBX) - ColorDH) - Red vaCH) - GreenCl) - Blue v

Al) = 11H - Rese


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Al) = 14H - Reser

Al) = 15H - ReadBX) - Color


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For Personal System 2

AL) 00H

BX) = 0712H

AL) = 01H to 02H


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Al) = I7H ReadES:DX) Poi

Tabgree

BX) First cCX) Number


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AL) = 03H - SetBL) - Chara

CharactBL)Charact

BL)


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Al) = 10H - UserES:BP) - Poi

CX) - CountDX) - CharactBl) - BlockBH) - Number


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On Return:CX) - Points

OL) - RowsES:BP) - Point



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AL) = 04H - RO 8xBL) - Block t

Register values AL) =AL) OOH 01H, 02H, and


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Al) = 14H - ROBl) - Block

Al) = 20H - SetES:BP) - Po

Al) = 21H - Set


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AL) = 00H - User a

ES:BP) - PoinCX) - Count tOX) - CharactBL) - Block tBH) = 16 byte


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A block specifier commandcharacter load command tocharacter set.

Al) = 04H - ROBl) - Block


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Al) = 24H RO 8xBl) - Row sp

Note: AL) 20H, 21 Himmediately after a


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For Personal System/2 prod

BL) 30H - Sele

TakAL) = 0 - 21 - 3

= 2 - 4


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Note: When enabled, summMode) color registerRegisters).

BL) 34H - CursorAL) = 0 - Ena

1 Di


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On Return:AL) = 12H Fu

BL) = 34H Rese

Note: When enabled, suM d ) l i


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The following steps in

1. Initial adapter vid2. Initial system boa

The initiate display swtim switching is initswitching between the


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AL) = 00HBL) - Attrib

String

AL) = 01HBL) - AttribString

AL) = 02H


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AL) = 03H to FFH -

For all others no action is p

AH) = 15H - Return PhysDisplay

F PC C tibl


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AH) 1 AH - Read/Writ

For Personal System/2 prod

AL) = 00H - Read

On Return:


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AH) = 1BH - Return Func


BX) - ImplementatES:DI) - User buff

O Return:


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DI+2BH) byte - PP

= 0= 1

= 2

= 2


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DI+32H) byte - SaBits Bit 5Bit 4

Bit 3Bit 2Bit 1Bit 0


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03H) to 07H)

07H) byte SBitBit Bit Bit


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0EH) byte - SaBitsBit 5

Bit 4Bit 3Bit 2


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On Return:AL) = lCH Fu

Requested

Supported save/res

Bi 5 3 R


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Interrupt H Equipme

This routine returns the optionasystem. BIOS data area 40:10 POST as follows:


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Interrupt 12H Memory

This routine returns the amountdetermined by the POST mExtended BIOS Data Area. See


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Interrupt 13H Diskette

This interface provides access tsummary of the diskette funct


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On Return:CF = 1 - Status

= 0 - Status

AH) - Status of = 80H - Dis= 40H - See= 20H - Gen= 10H C


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AH) = 02H - Read Desir

Dl) - Drive numbBit 7 0 - D

DH) - Head numbeCH) - Track numbCl) - Sector numAl) Number of s


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Notes:

1. If an error is reportesystem, then retry the

2. For PC XT Model 28

AH) = 04H Verify Desir


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Byte 3 - Number o= 99H - 12= 91H - 25= 92H - 51

= a3H - 19

There must be one entry


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AH) == 08H Read Drive

There is a parameter table

For PCjr PC, PC XT, or

On Return:


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If the requested rive is(DI), and ES) = o.

Diskette status 40

For drive number 80H o


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For all others:

On Return:CF = 1 - ErrorAH) - Status of

= 01H - Inv

Diskette status at


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When the diskette change diskette is changed, this fu

For PC XT BIOS dated 1

Personal System 2 prod

OL) - Drive numbeBi 7 0 D


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Interrupt 13H Fixed D

This interface provides access summary of the fixed disk f


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function. There is no cMultitasking Provisions

5 Bit 7 of the drive number m

BIOS.6 For the drive parameters se

on page 3-16


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Notes:

1. An 11H rror indicathat was corrected by

good; however, thethe controlling progrr ror may not recur


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= 0 - StatusAH) - Status of

operation

Note: If an error is rep


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For the IBM ESDI Fixed D

On Return:AH) - Status of

CF 1 - Error


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AH) = 07H - Format Driv

For PC XT:

Dl) - Drive numbeCH) - Cylinder num

0-based, no


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AH) = 09H - Initialize

DL) - Drive numb


= 0 - Status


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AH) = OAH to OBH - Re

AH) = OCH - Seek

DL) - Drive numbeDH) - Head numberCH) - Cylinder num

0-based, not


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On Return:CF 1 - Status

0 - StatusAH) - Status of

operation

AH) H - Recalibrate


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(AH) = 16H to 18H - Reser

(AH) = 19H - Park Heads

For PC XT, AT, and PC XT M

On Return:AH) - Status of o


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An INby BIforma

The hfor enumbin gr


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Interrupt 14H - Asynchr

These routines provide RS-232summary of the RS-232-C supp


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On Return:AL) - Modem st

Bit 7 - ReBit 6 - Ri

Bit 5 - DaBit 4 - CleBit 3 - DeBit 2 - Tra


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AH) = 03H - Read Status

OX) - RS-232-C coto actual po

On Return:Al) - Modem stat


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On Return:AL) - Modem staAH) - Line statu

For all others no action

AH) 05H - Extended Co


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Interrupt 15H - System S

The following is a summary

AH) = OOH - Turn Cassette MotAH) 01 H T C M


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For all others:

On Return:AH) = 86H

CF = 1


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AH) = 3H - Write Bloc

For P jr and PC:

ES:BX) - Pointer tCX) - Count of by


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For PCjr and PC:

On Return:AH) = 80H

CF 1

For all others:


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For all others:

On Return:AH) = 86H

CF = 1

AH) = 22H to 3FH - Rese


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For all others:

On Return:AH) = 86H

CF = 1

AH) = 41 H - Wait for Ex


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For all others:

On Return:AH) = 86H

CF = 1

AH) 42H - Request Sys


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For PC Convertible:

On Return:AL) - Status

Bit 7 - LowBit 6 - OpBit 5 - StaBit 4 Pow


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AH) = 45H to 4EH - Re

AH) = 4FH - Keyboard

For P jr and PC:

On Return:

(AH) = 80H


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AH) = 80H - Device Op

For PCjr and PC:

OnReturn:AH) = 80H

CF = 1


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AH) = 82H - Program Ter

For P jr and PC

On Return:AH) = 80H

CF 1


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For all others:

AL) = 00H - Set iES:BX) - Pointer t

the highinterval

CX OX) - Microsec


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On Return:AX) A{x valuBX) A{y valuCX) B{x valueDX) B{y valu

CF = 1 Invalid ca


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For all others:

CX,DX) - Time befGranula

CF = 0 - Successful = 1 - Wait func


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On Return:AH) = 00H - OpeAH) = 01H - R MAH) = 02H - OthAH) = 03H - Gat

All


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The fourth pOints to thinitialized.

The fifth is used by thcode segment. It is uby the BIOS.

The sixth is used by th


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For AT, PC XT Model 286Model 30, this routine retbeginning at address 10000system may not be able to

board is fully populated.

On Return:


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The following shows the opointed to by ES:SI):

E S : S I ) ~ 00

u

08


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The seventh pOints to returns to the user, in

The eighth is used to is necessary for this fin the protected modecode, this descriptor c


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AH) = 8AH to 8FH - Rese

AH) = 90H - Device Busy

For PCjr and PC:

On Return:AH) = 80H


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On Return:CF = 0 Wait n

= 1 Minimthis t

AH) = 9 H - Interrupt C


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For AT BIOS dated 6 10and after PC XT Model System 2 products:

AH) = C0H

On Return:


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For PC XT, AT, PC XT M

On Return:AH) = 86H

CF = 1

For all others:


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Al) = 01H Reset

On Return:See Return for

f the operation sucBH) Device ID

00H


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On Return:See Return for

f the operation suBH) Devi ce ID

=00H

AL) = 0SH Poin


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Cl) -====

DL) -


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Word 1 on stack:ow byte Status

Bit 7 Y data= 1 O

Bit 6 X data= 1 O


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AH) = C3H - Enable/Dis

For PCjr and PC:

On Return:AH) = 80H

CF = 1


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For Personal System/2 produ

AL) = 00H Retur

On Return:AL) = 00HOX) Base POS


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Interrupt 16H Keyboar

These routines provide keyboasummary of the keyboard func


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f the extended functions are supp

I The character code placed ininterrupt handler differentia

nomenclature.I The keyboard interrupt hand


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See Scan Code/Character Codscan code/character code comb

(AH) = OOH -Keyboard

The scan code/character ckeyboard buffer head poin


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AH) 02H - Shift Status

On Return:AL) - Current s

Bit 7 = 1 -Bit 6 = 1 -Bit 5 = 1 -Bit 4 1

F AT BIOS d t d 11/15/85


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For AT BIOS dated 11/15/85 Personal System/2 products:

Al) = 05H - Set typBl) - Typema00H = 30.001H = 26.702H = 24 0


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Cl) ASCII charaCH) Scan code

On Return:Al) = 00H Op

= 01H Buf

F ll th ti i


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For all others no action is pe

AH) = 12H - Extended Sh

For T BIOS dated 11 15after, PC XT Model 286, an

On Return:


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AH) 02H R d St t


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AH) = 02H - Read Status

DX) - Pr inter totable t 40

On Return:AH) - Status

l


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6. For Personal System 2printer port associated wAH) is returned unchange


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Interrupt 19H Bootstra

Track 0 se tor 1 is read intotransferred as follows:


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AH) = 03H - Set Real-Ti

For AT, PC XT Model 2products:

CH) Hours in BCl) Minutes in

AH) = 06H Set Real Tim


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AH) = 06H - Set Real-Tim

For AT, PC XT Model 286products:

CH) Hours in BCCl) Minutes in BDH) Seconds in B

d d


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For AT BIOS dated 6 10Personal System 2 pro

On Return:

CF = 1 Invalid

For PC XT BIOS dated 1/1


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For PC XT BIOS dated 1/1products:

On Return:CX) - Count of d


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Interrupt 70H Real Tim

For AT, PC XT Model 286 an

This interrupt handler cont


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Section 3 Data r

BIOS Data Area

E d d BIOS D A

Notes:


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Notes:


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BIOS Data rea

The BIOS Data rea is allo

system BIOS and adapter BIOSmemory from absolute addres

f


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Address Function

40:10 Installed Hardwar

Bits 15,14 Number of PrinBit 13 ReservedBit 12 ReservedBits 11,10,9 Number of RS-2Bit 8 Reserved


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Address Function

4 :17 Keyboard Control

Bit 7 Insert LockedBit 6 Caps Lock LockBit 5 Num Lock LockBit 4 Scroll Lock LocBit 3 Alt Key Pressed


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Address Function

40:3E Recalibrate status

Bit 7 Interrupt FlagBit 6 ReservedBit 5 ReservedBit 4 ReservedBit 3 Recalibrate Driv


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Address Function

40:49 Display Mode set40:4A Number of Colum40:4C Length of Regen40:4E Start ing Address i40:50 Cursor Position Pa40:52 Cursor Position P40:54 Cursor Position P


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Address Function

40:71 Break Key State40:72 Reset Flag

1234H = By4321H = Prproducts exc5678H S


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Address Function

40:78 Printer 1 Time-out40:79 Prin ter 2 Time-out40:7A Prin ter 3 Time-ou40:7B Reserved

Exceptions


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Address Function

40:8B Media Control

Bits 7,6 Last Diskette DrivBinary)

= 500Kb 1 = 300Kb


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ddress Function

40:96 Keyboard Mode S

Bit 7 Read 10 in ProBit 6 Last Character

Bit 5 Force Num LocBit 4 101/102-Key KBit 3 Right Alt Key P

For systems with EGA capabili


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y psave pointer table contains poverrides for the video mode

Address

40:A8

Function

Pointer to Video

Address Function


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Address Function

Displayable

Bytes Per Ch

Pointer to a

Consecutive

Address Function


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Address Function01,08 Entr00,07 Entr02,07 Entr02,06 Entr

AbbreviatioMDPA = MAdapter

dd F i


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Address Function

Internal PaleOperation)

Pointer to I

External PalOperation)


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For AT and Personal System/2


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isk rive parameters for thare decimal unless noted otherw

Number of NumberType Cylinders of Heads

4. PC XT Model 286 contai


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5. Personal System/2 producthrough 32.

6. Personal System/2 Model

For Personal System/2 product

For PC XT BIOS dated 11/10/8


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p r meter tables apply:

Size Value

DW 0306DB 02

Descripti

MaximumMaximum


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Size Value

OW 3 6DB 6OW 128

OW 256DB OBHDB 5H

Descrip

MaximuMaximuStart Re

Start WMaximuControl

For PC XT BIOS dated 1/08/8


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parameter tables apply:

Size Value

OW 306DB 4

Descrip

MaximuMaximu


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Size Value

DW 615DB 4DW 615

DW 300DB OBHDB 05H

Descript

MaximuMaximuStart Red

Start WrMaximuControl

iskette rive Parameter Table


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The diskette drive parameter ta

Offset Length Descriptio

Notes:


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Section 4. ddition

Interrupt Sharing

Notes


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nterrupt Sharing

This section defines an intehardware adapters on theto share a single interrupt requ

Interrupt handler impleme


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using Intel TM format; thain memory.

Interrupt Request IRQn) R

h h l

To link an interrupt handler, th


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handler replaces the interrupt its own interrupt handler. (Seefor interrupt handlers stored inpreserve the interrupt vectorpointer to the next interrupt havector must be stored at a fixed

During a system-reset conditionb d f


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must be executed after power-oresponsible devices.

Operating system environments

software must manage the entirhandler software written exclu

flag 80H) in the FLAGS byte


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chain.

The Reset routine, an entry podis ble the adapter interrup

d

MOV CS:[SI+2],


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CMP ES:BYTEPTi f iret_test_only_is_needed

JNE SETVECTRelse

JECMP FRSTVCTRES: WORDP

FIRST is allowed onlyi l d d


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system is loaded.

Interrupt Handler

YOUR_CARD EQU xxxx

MYCSEG ENDSEND ENTRY


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ENTRY

Unlinking

PUSH OS

JMP UNCHAIN_

UNCHAIN B MOV BX SI


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UNCHAIN_B MOV BX SIPUSH DS

POP ESJMP UNCHAIN_

UNCHAIN_X STI

POP ESPOP DS


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For Personal System/2 products,d h d


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a ROM signature code that identPOST, when CMOS is not vcode is used to find the first viprogrammable option select PO

The code starts at OCH in th

Vid F i i


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Video Function ompati

The following procedures are re

compatibility to application sof


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ultitasking Provisions

The BIOS provides hooks to ass

Whenever a busy Wait) loop ocfor the program to break out of


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MOV AX 9 xxH ;Wait cod; type co

INT 15H ;Issue caJC TIMEOUT ;Optional:

; i carr; occurred

NORM LTIMEOUT LOGIC ;Normal t


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System dentification

Each BIOS ROM module has a

ROM. In some cases a submodeare used to further dist inguish t

li i G id li


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pplication Guidelines

Use the following information

IBM Personal System 2 andpossible, BIOS should be u

lI commands followed immpermit enough recovery tim


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permit enough recovery timoperations. To ensure enough tinserted between the lI co

Notes:

Programming Consideratio


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The IBM-supported languageand Pascal are the best choiceprogram uses specific feature

not be compatible with all IBComputer products

another parameter block a0:78) to point to the new b


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0:78) to point to the new b

The parameters were estab

Some models of the IBthe 5.25-inch high cap

Programs may be designe3 5-inch diskettes Since


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3.5 inch diskettes. Since dependent, the following type of media inserted int

1. Verify track 0, headBIOS to determine if

Scan Code Character Code Co


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Scan Code Character Code Co

The followi ng I sts the keyboacode/character code combinatio

83 anStand


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StandKeystroke Funct

\ 28/5Cz 2C/7Ax 20/78

c 2E/63v 2F/76

83- aStan


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StanKeystroke Funct

Right Arrow (no kEnd (no kDown Arrow (no k

PageDown (no keInsert (no k

83- aStand


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StandKeystroke Functi

Shift A 1E 41Shift S 1F 53Shift D 20 44

Shift F 21 46Shift G 22 47

83- anStand


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StandKeystroke Functi

Shift 3 51/33 Shift 0 52/30Shift . 53/2E

Shift SysReqShift Key 45 no k

83- aStand


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StandKeystroke Func

Glrl w ETB) 11/17Gtrl e ENQ) 12 05Gtrl r OG2) 13/12

Gtrl t OG4) 14/14Glrl y EM) 15/19

83 anStand


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Sta dKeystroke Function

Gtrl Num LockGtrl Scroll LockGtrl Home 77/00

Gtrl Up rrowGtrl PgUp 84/00

The following lists the Alt keycode/character code combinati


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code/character code combinati

83-Stan

Keystroke Funct

Alt Esc

83- aStand


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Keystroke Funct

Alt n 311Alt m 32 00Alt,

Alt .Alt

For all keyboards, the numeriwith the Alt key to input any A


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t e t ey to put a y00) and character code are retuexample, pressing lt and Kcode/character code combinati

255, then releasing lt returhex OO/FF

Notes


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Glossary

This glossary includes terms anddefinitions from the IBM Voca

per second in Morse code, and 3-bit value per second in a traisignals each of which can assume


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signals each of which can assumeone of eight different states.asynchronous transmission, the unof modulation rate corresponding

one unit of interval per second;is, if the duration of the unit in

character generator. 1) Incomputer graphics, a functional


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that converts the codedrepresentation of a graphiccharacter into the shape of thecharacter for display. 2) In

processing, the means withini f i i

cyclic redundancy check CRC).1) A redundancy check in whichh h k k i d b


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the check key is generated by acyclic algor ithm. 2) A system oerror checking performed at boththe sending and receiving station

after a block-check character hbeen accumulated


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hertz (Hz). A unit of frequencyequal to one cycle per second.


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hex. Common abbreviation forhexadecimal.

hexadecimal. 1) Pertaining tol ti h i diti

the transmitting station to terma transmission. 3) Synonym


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with interruption.

1/0 Input/output.

1/0 area. Synonym for buffer

designed for use with othercomponents.


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monitor. Synonym for cathode tube display CRT display).

ms. Millisecond; 0.001 second.

programmable read-only memoryPROM). A read-only memory

can be programmed by the use


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can be programmed by the use

programming language. 1)artificial language established

expressing computer programs2) A set of characters and ru

SOLe. Synchronous Data LinkControl.


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sector. That p rt of a track oron a magnetic drum a magneticdisk or a disk pack that can be

accessed by the magnetic heads inthe course of a predetermined

accessible to a given reading heaposition


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window. 1) A predefined pthe virtual space 2) The visarea of a viewplane

d 1) A h i

Notes


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Index


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Index

A


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set real time clock timeset system timer day

t 2 120


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counter 2-120set system timer time

counter 2-116set up sound multiplexer

INT 10H video) 2-10l l 2 32

device open 2-83enable/disable watchdog

time out 2 102


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time-out 2-102event wait 2-84extended memory size

determine 2-89

format unit periodici t t 2 76

keyboard interrupt 09H) level-sensitive interrupts

i d t i ti


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memory size determination12H) 2-47

NMI 02H) 2-4nonmaskable interrupt

02H) 2-4i 05H) 2 6

read status 2-112printer port base address data

area 3 3


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area 3-3printer time-out value data

area 3-8program termination 2-84

programmable option selectPOS) 2 102

set system-timer timecounter 2-116

set typematic rate 2-107


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set typematic rate 2 107set up sound multiplexer 2-1sharing, interrupt 4-3

implementation information

interrupt request 4-4interrupt sharing chaining

set system-ti mer daycounter 2-120

set system-timer time


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set system timer timecounter 2-116

set up sound multiplexersystem timer data area 3-7


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_


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PS2 and PC BIOS Interface Technical Reference Apr87

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