IBM PC CONVERTIBLE Technical Reference page 196

WAIT ON
TIME INTERVAL: AH = S6H
DEVICE BUSY:
DEVICE
INTERRUPT
COMPLETE:
READ SYSTEM
DESCRIPTION
TABLE
CX,DX NUMBER OF MSECONDS
TO ELAPSE BEFORE RETURN
TO CALLER
AH = 90H
AL = DEVICE TYPE (SEE CODE)
01 - DISKETTE
02 - KEYBOARD
03 - FFH ALL OTHERS
RETURN AFTER TIME
ELAPSED XXX
RETURN AFTER IRPT
RECEIVED OR 2 SECOND
TIMEOUT HAS OCCURRED
CARRY SET I F TIMEOUT
RETURN WHEN KEYBOARD
BUFFER TAIL
<>
CURRENT VALUE
IMMEDIATE RETURN
AH = 91H IMMEDIATE RETURN
AL = DEVICE TYPE
OOH
->
7FH
SERIALLY REUSABLE DEVICES
OPERATING SYSTEM MUST SERIALIZE
ACCESS
SOH
->
BFH
REENTRANT DEVICES; ES:BX IS
USED TO DISTINGUISH DIFFERENT
CALLS (MULTIPLE I/O CALLS ARE
ALLOWED SIMUL TANEUSLY)
COH
->
FFH
WAIT ONLY CALLS; THERE IS NO
COMPLEMENTARY 'POST' FOR THESE
WAITS - - THESE ARE TIMEOUT
ONLY. TIMES ARE FUNCTION NUMBER
DEPENDENT.
DEVICE TYPE DESCRIPTION TIMEOUT
OOH = DISK YES
01H = DISKETTE YES
02H = KEYBOARD NO
FDH = DISKETTE MOTOR START YES
AH=O, CARRY CLEAR
ES: BX TABLE POINTER
AH = COH
TABLE
BYTE
DEFINED AS FOLLOWS:
1&2: LENGTH OF TABLE IN BYTES
BYTE
BYTE
BYTE
BYTE
STARTING AT BYTE 3
3: SYSTEM MODEL BYTE
4: SECONDARY MODEL BYTE
5: BIOS REVISION NUMBER
6: FEATURE INFORMATION BYTE 1:
MSB:
BIT 7 = 1 -
o -
BIT 6
=
1 -
o -
BIT 5 = 1 -
o -
BIT 4 = 1 -
BIOS USES DMA CHANNEL 3
DMA CHANNEL 3 NOT USED
2ND INTERRUPT CONTROLLER INSTALLED
2ND INTERRUPT CNTLR NOT INSTALLED
REAL TIME CLOCK PRESENT
REAL TIME CLOCK NOT PRESENT
INT 15H FUNCTION 4FH LINKAGE FROM
BIOS INT9 SUPPORTED
o -
LI NKAGE NOT SUPPORTED
Bi t 3 = 1 - INT 15H FUNCTION 41H WAIT ON
EXTERNAL EVENT SUPPORTED
o -
INT 15H FUNCTION 41H NOT SUPPORTED
Bit 2-0= RESERVED
BYTES
7-10: RESERVED FOR FUTURE FEATURE EXPANSION
ROM BIOS 2-171