IBM 5170 Technical Reference page 299

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-----THE-G~Oa;l- DESCRIPTOR -T;BLE-(;c;:u;L-Loc~ ;:'ON-;OINTED-TO-BY-Es;sij
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-
-­
--­ --­
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----------------------------------------- ­
VI RTUAL_ENABLE_GOT _OEF STRUC
0000 00
00
00 00 00
00
00 00
OUMY OQ
FIRST DESCR
j
PTOR NOT ACCESS I BLE
0008 00 00 00 00 00 00 GOTPTR OQ GOT OEseR I PTOR
00 00
0010 00 00 00 00 00 00
j
OTPTR
00
lOT DESCRIPTOR
00 00
0018 00 00 00 00 00 00
USER_DS
00
USER DATA SEGEMNT DESCRITOR
00 00
0020
00 00 00 00 00 00 USER_E5
00
USER EXTRA SEGMENT DESCRI PTOR
00 00
0028 00 00 00 00 00 00 USER_SS 00
USER STACK SEGMENT DESCRI PTOR
00 00
0030 00 00 00 00 00 00 USER_CS OQ USER CODE SEGMENT OEseR I PTOR
00 00
0038
00 00 00 00 00 00 BIO_CS DQ TEMPORARY B I OS DESCR I PTOR
00 00
0040 V I RTUA~ENABLE_GOT_DEF ENDS
;
-- ­ -­
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--­
----_
.....
----­
-
--
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..
-­
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....
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---
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-
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---­
ASSUME CS:CODE
~
ASSUME OS: DATA
03£6 X_VIRTUAL PROC
FAR
03E6 SET_VMODE:
03£6
FA
ell NO INTERRUPTS ALLm.tED
;-_ .... --­ ENABLE ADDRESS LATCH BIT 20
03E1 84 OF MOV AH, ENABLE_B I T20 ENABLE BIT 20 FOR ADDRESS GATE
03E9 E8 03BO R CALL GATE_A20
03EC
03EE
3C
74
00
04
eMP
JZ
AL,O
BIT20_0N
WAS THE COMMAND ACCEPTED?
GO I F YES
03FO 84 FF
MOV AH,OFFH SET THE EMOR FLAG
03F2 F9 STe SET CARRY
03F3 eF
IRET EARLY EXIT
03F4 B I T20_0N:
SECOV
ES
LOAD THE GLOBAl.. DESCR I PTOR TABLE REG
03F4 26
DB 026H
03FS OF
+
LGDT (SIJ.GDTPTR
OOFH DB
03F6
: 170015
LABEL
BYTE
03F6
03F9
88 54 08
+
MOV
LABEL
OX, WORD PTR (S I J. GDTPTR
BYTE
110016
03F6
+
ORG OFFSET CS: 710015
03F6
01
+
DB 001H
03F9
+
ORG OFFSET CS:770016
SEGOV ES LOAD THE INTERUPT DESCRIPTOR TABLE REG
03F9
26
DB 026H
03FA OF
+
LIDT
DB
[Slj.IDTPTR
OOFH
03FB
03FB
03FE
8B 50 10
:
:
1?0018
1?0019
LABEL
MOV
LABEL
BYTE
BX, WORD PTR (S I
J.
IOTPTR
BYTE
03FB
ORG OFFSET CS:110018
03FB 01 DB 001H
03fE
ORG OFFSET CS:710019
;
--- ­ ---­
-
-- --_
..
_
....
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_
.. _.
--­
..
~
-­
~
_
..
_
..
_--­ ---­
_
..
--­
--­ ----­ ---
-- ­
03FE BO 11
MOV AL,11H START INITIALIZATION SEQUENCE-ICW1
r"\
0400
0'j02
0404
01106
0408
E6
EB
8A
E6
EB
20
00
C7
21
00
OUT
JMP
MOV
OUT
JMP
rNTAoo,AL
SHORT $+2
AL,BH
INTA01,AL
SHORT $+2
EDGE, INTERVAL-8,MASTER.ICW4 NEEDED
HARDWARE INT'S START AT INT
/I
ISH)
SEND ICW2
040A
BO 04 MOV AL,04H SEND I cwa - MASTER I..EVEI.. 2
040C
040E
E6
EB
21
00
OUT
JMP
~~6~~1 s:~
0410 BO 01 MOV AL,01H SEND I CW4 - MASTER,8086 MODE
0412
0414
E6
EB
21
00
OUT
JMP
I NTAOl ,AL
SHORT $+2
0416
0418
BO
E6
FF
21
MOV
OUT
AL,OFFH
INTA01,AL
MASK OFF ALL INTERRUPTS
--~----------------------~
..
------------------ ..
--------_
..
_------------------
..
-
I
~
REINITIALIZE THE 8259 INTERRUPT CONTROLLER #2 TO THE usER SPECIFIED OFFSET
041A BO 11 MOV AL,llH ; START I NIT SEQUENCE-I CW1 FOR SLAVE
BIOS 1 5-157