IBM PC CONVERTIBLE Technical Reference page 214

0435 B7 80
MOV BH,INLFLAG INTERRUPT COMPLETE FLAG
0437 BO 03
MOV AL,03 FN CODE = TEST, RETURN NOT 0
0439 B3 25 MOV BL,25H SET TWO SECOND TIMEOUT
043B BUSLWAIT:
043B
E8 01BE R
CALL EXLEVENT
043E
DEVB_EXIT:
043E 5B POP BX
043F
07 POP ES
0440 5F
POP 01
0441 C3 RET
0442
DEY-BUSY ENDP
---------------------------------------------------------------------
INT 15H
ROUTINE-NAME: TMRO_CHK
FUNCTION: THIS ROUTINE CHECKS TO SEE I F TIMER 0 IS SET UP AS FOLLOWS
IRPT ENABLED TIMER COUNTING INT 8 VECTOR=TMRO_INT8 ADDR
INPUT: NONE.
OUTPUT: CARRY FLAG SET - TIMER IS RUNNING
CLEAR - TIMER NOT RUNNING
REGISTERS
MODIFIED: NONE.
----------------------------_
....
_-------------------------------------
ASSUME DS:ABSO
0442
TMRO_CHK PROC NEAR
0442
50
PUSH AX
0443 53 PUSH 8X
0444 1E PUSH OS
0445 88 0000 MOV AX,O
0448 8E 08 MOV DS,AX
044A A1 0020 R MOV AX,INT...ADDR GET INT 8 OFFSET ADDRESS
0440 1F POP OS
044E 3D 0000 E CMP AX,OFFSET TMRO_INT8 CHECK FOR OUR TIMER ROUTINE
0451 75 1B JNE TMRO_NORUN IF NOT THEN EXIT
0453 E4 21 IN AL,INTA01
0455 A8 01 TEST AL,Ol CK FOR TMR 0 I RPT ENABLED
0457 75 15 JNE TMRO_NORUN EXIT IF DISABLED
0459 E4 40 IN AL, TIMERO MAKE SURE TIMER IS RUNNING
045B 8A EO MOV AH,AL
0450 E4 40 IN AL, TIMERO
045F 50 PUSH
AX
SAVE CURRENT TMR 0 TIME CNT
0460 58 POP 8X RETRI EVE ORIGINAL COUNT
0461 E4 40 IN AL, TIMERO RE-READ TIMER LOW
0463 8A EO MOV AH,AL
0465 E4 40
IN AL, TIMERO RE-READ TIMER HI
0467 38 C3
CMP AX,8X COMPARE WITH ORIGINAL
0469 74 03 JE TMRO_NORUN JUMP I F TIMER NOT RUNNING
046B TMRO_OK:
0468 F9
STC
SET CARRY TO INDICATE OKAY
046C EB 01
JMP
SHORT TMRO_EXT
046E TMRO_NORUN:
046E F8 CLC CLEAR CARRY
046F
TMRO_EXT:
046F 58 POP 8X RESTORE REGS
0470 58 POP AX
0471 C3 RET
0472
TMRO_CHK ENDP
ROM BIOS 2-189