IBM 5150 PC Technical Reference (6025005, August, 1981) (PDF)

lOC OBJ LINE SOURCE
5641 ;--- INT lA ------------------------------­
5642 TIME_OF _DAY
5643 THIS ROUTINE ALLOWS THE CLOCK TO BE SET/READ
5644
5645 INPUT
5646 IAH) = 0 READ THE CURRENT CLOCK SETTING
5647 RETURNS ex = HIGH PORTION Of COUNT
5648 OX = lOW PORTIOt~ Of COUNT
5649 AL = 0 IF TIHER HAS NOT PASSED 24 HOURS SINCE LAST READ
5650 0 IF ON ANOTHER DAY
5651 IAH) = 1 SET THE CURRENT ClOCK
5652 CX = HIGH PORTION OF COUUT
5653 OX = LOW PORTION OF COUNT
5654 NOTE: COut-ITS OCCUR AT THE RATE OF 1193180/65536 COUIITS/SEC
5655 lOR ABOUT 18.2 PER SECOND -­ SEE EQUATES BELOW)
5656 ; -------­----------­-----------------­------­
5657 ASSUME CS:CODE.DS:DATA
FE6E 5658 TIME_OF_DAY PROC FAR
FE6E Fe 5659 STI INTERRUPTS BACK ON
FE6f IE 5660 PUSH DS SAVE SEGMENT
FE70 50 5661 PUSH AX SAVE PARN
FE7l 884000 5662 MOV AX.DATA
FE74 8E08 5663 MOV DS.AX I ESTABLISH ADDRESSING TO VALUES
FE76 56 5664 POP AX i GET BACK INPUT PARM
FEn OAE4 5665 OR AH.AH ; AH=O
FE79 7407 5666 JZ T2 ; READ_TIME
FE7B FEee 5667 DEC AH I AH=1
FE7D 7416 5668 JZ n ; SET_TINE
FE7F 5669 Tl: ; TOO_RETURN
FE7F FB 5670 STI ; INTERRUPTS BACK ON
FEeD IF 5671 POP os ; RECOVER SEGMENT
FEel CF 567Z IRET ; RETURN TO CAllER
5673
FEel 5674 12: I READ_TIME
FEez FA 5675 CLI ; NO TIMER INTERRUPTS WHILE READING
FEB3 A07000 5676 MOV AL.TINER_OFl
~ FE86 C606700000 5677 MOV TIMER_OFL.O ; GET OVERFLOW. AND RESET THE FLAG
FEes 860E6EOO 5678 MDV CX. TIMER_HIGH
FE8F 88166COO 5679 MOV OX. TIMER_LOW
FE93 EBEA 5680 JMP Tl
5681
FE 95 5682 T3: SET_TIME
FE95 FA 5683 CLI NO INTERRUPTS WHILE WRITING
FE96 69166COO 5684 MOV TINER_LOW. OX
FE9A 890E6EOO 5685 MOV TIMER_HIGH .CX SET THE TIME
FE9E C606700000 5686 MOV TIMER_OFl.O RESET OVERflOW
FEU EBDA 5667 JMP Tl TOO_RETURN
TIME_OF _DAY
568~ ; -------­----------­-­----------------------­
5690 ; THIS ROUTINE HANDLES THE TINER INTERRUPT fROM
56~1 ; CHANNEL 0 OF THE 8253 TIMER. INPUT FREQUENCY IS 1.19318 HHZ
5692 ; AHD THE DIVISOR IS 65536 , RESULTING IN APPROX. 18. Z INTERRUPTS
5693 ; EVERY SECOND.
5694
5695 THE INTERRUPT HANDLER MAINTAINS A COUNT OF INTERRUPTS SINCE POWER
5696 ON TIME. WHICH MAY BE USED TO ESTABLISH TINE OF DAY.
5697 THE INTERRUPT HANDLER ALSO DECREMENTS THE MOTOR COtHROl COUNT
5698 OF THE DISKETTE, AND WHEU IT EXPIRES, WILL TURN OFF THE DISKETTE
5699 NOTOR. AND RESET THE MOTOR RU~INING FLAGS
5700 THE INTERRUPT HAf'..'OLER WILL ALSO INVOKE A USER ROUTINE THROUGH INTERRUPT
5701 lCH AT EVERY' TIME TICK. THE USER MUST CODE A ROUTINE AND PLACE THE
5702 CORRECT ADDRESS IN THE VECTOR TABLE.
5703
HAS 5704 TIMER_INT PROC FAR
FEAS Fe 5705 STI ; INTERRUPTS BACK ON
~FEA61E 5706 PUSH DS
FEA7 50 5707 PUSH AX
FEAB 52 5708 PUSH DX ; SAVE MACHINE STATE
FEA9 884000 5709 MDV AX.DATA
FEAC BED8 5710 MOV DS,AX ESTABLISH ADDRESSABIlITY
FEAE FF066COO 5711 INC TIMER_lOW INCREMENT TIt1E
FEBZ 7504 5712 JIIZ T4 TEST_DAY
FEB4 FF066EOD 5713 INC TIMER_HIGH UICREMENT HIGH WORD OF TIME
FEBS 5714 T4: TE!"T_DAY
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