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LI NE
SOURCE
(B I OS FOR THE I BM PERSONAL COMPUTER XTl
1 1 /08/82
5-173
I NTERRUPTS BACK ON
RESET MACHINE STATE
RETURN FROM INTERRUPT
01 SKETTE_CTL
RETURN I F COUNT NOT OUT
TURN OFF MOTOR RUNN I NG BITS
FDC CTL PORT
TURN OFF THE MOTOR
TIMER RET:
TRANSFER CONTROL TO A USER ROUT I NE
END OF I NTERRUPT TO 8259
SAVE MACHINE STATE
INCREMENT T I ME
TEST DAY
INCREMENT HIGH WORD OF T I ME
TEST DAY
TEST-FOR COUNT EQUAL I NG 24 HOURS
01 SKETTE_CTL
01 SKETTE_CTL
FAR
lCH
AL.EOI
020H.AL
ox
AX
OS
AX.AX
TIMER HIGH.AX
T I MER-LOW. AX
T I MER=:OFL. 1
ENDP
MOTOR COUNT
T6
-
MOTOR STATUS.OFOH
AL.
ocR
ox
.03F2H
DX.AL
T I MER HIGH. 0 18H
T5
-
T I MER LOW. OBOH
T5
-
OFEA5H
PROC
OS
AX
OX
DDS
TIMER LOW
T4
-
TIMER_HI GH
PC-XT System BIOS (11/08/82)
DEC
JNZ
AND
MOV
MOV
OUT
SUB
MOV
MOV
MOV
CMP
JNZ
CMP
JNZ
THE INTERRUPT HANDLER MAINTAINS A COUNT OF
INTERRUPTS
SINCE POWER ON TI ME.
WH
I CH MAYBE USED TO ESTABLI SH
TIME OF DAY.
THE
I NTERRUPT HANDLER ALSO DECREMENTS THE MOTOR
CONTROL COUNT OF THE 0 I SKETTE. AND WHEN IT EXP I RES.
WILL TURN OFF THE 0 I SKETTE MOTOR.
AND RESET THE
MOTOR RUNN I NG FLAGS.
THE I NTERRUPT HANDLER WILL ALSO I NVOKE A USER ROUT I NE
THROUGH INTERRUPT 1CH AT EVERY T I ME TICK.
THE USER
MUST CODE A ROUTI NE AND PLACE THE CORRECT ADDRESS
IN
THE VECTOR TABLE.
TH I S ROUT I NE HANDLES THE T I MER I NTERRUPT FROM
CHANNEL 0 OF THE 8253 T I MER.
I NPUT FREQUENCY
l S I . 19318 MHZ AND THE 0 I V I SOR
IS 65536. RESULT I NG
IN APPROX.
18.2 I NTERRUPTS EVERY SECOND.
;------ TEST FOR DISKETTE TIME OUT
INT
MOV
OUT
POP
POP
POP
IRET
TIMER
INT
;------ TIMER HAS GONE 24 HOURS
ORG
TIMER
INT
-
STI
PUSH
PUSH
PUSH
CALL
INC
JNZ
INC
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
T4:
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
T5:
5721
5722
5723
5724
5725
5726
5727
T6:
5728
5729
5730
5731
5732
5733
5734
5735
5736
FEC5 2BCO
FEC7 A36EOO
FECA A36COO
FECD C60670000 1
LOC OBJECT
FED2
FED2 FEOE4000
FED6 750B
FED8 80263FOOFO
FEDD BOOC
FEDF BAF203
FEE2 EE
FEE3
FEE3 CD1C
FEE5 B020
FEE7 E620
FEE9 5A
FEEA 58
FEEB IF
FEEC CF
FEA5
FEA5
FEA5 FB
FEA6
1E
FEA7 50
FEA8 52
FEA9 E8ADFB
FEAC FF066COO
FEBO 7504
FEB2 FF066EOO
FEB6
FEB6 833E6EOO 18
FEBB 7515
FEBD 813E6COOBOOO
FEC3 7500
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