Intel 80287 User Manual

des.
limit
bale_low
b a I!_h I g h
a
•• ess
res
des.
80286 SYSTEM INITIALIZATION
Define layout of a
s t r u c
dw
dw
db
db
dw
ends
Offset of last byte In segment
Low 16 bits of 24-blt address
Hlgh,8 bit. of 24-blt addrels
,Access byte
Reserved wo'rd
'D e fin e 't h'e' fixe d G D T I! I e c tor, val u e s 1. 0 r the des c rip' tors ,t hat
de fin e 't hO EP ROM - ba,l! d tab I e I. B L D 2 86m us t be in. t r u ,c ted top I ace the
Int,o the GDT.
gdt_allas
equ
I "s I z'e
des 'c GDT (I)
I I date segm,ent
I,n
RAM'
for
I d t_alla.
equ 2"slze desc
GDH2)
I. data segment In RAM for
s tar t_ T S S_a I I a s
equ 3"slze desc
GDH3)
Is data segment In RAM for
s tar t_ t a I • equ 4,. 1,1 z e, des cf
.,
GDH4)
I.
TSS
for starting ta ••
s tar t_L D T _a I I BI
e q'u
5 " s,l z!
desc
GDHS)
Is da te segment
I n, RAM
for
Define machine Itatus word bit pOs'ltlonS,..
PE
MP
EM
DT_ACCESS
DS_ACCESS
I
2
4
Pro t e c t Ion en ab 'I e
Monitor procelsor extension
Emulate procelsor extension
values of de.crlptor byte.
equ 82,H
Access
byh value for
an LDT
equ 92H
Acce.s
byte
value for date segment
GDT
IDT
TSS
LDT
which
Is
g row .u p.
at level
o •
wrlteable
TS LA C C E S S
DPL
ACCESSED
T I
TSS_SIZE
LDT_OFFSET
T
1R P L_MA S K
equ
equ
equ
equ
e q'u"
equ
equ
81H
60H
I
4
44
42
• I z e
desc-I
.
Access
byte
val u'e
for an I die TSS
Privilege level
f1 e I,d of
a c,c e. s rights
Define acces.ed bit
Position of T I bit
Size
of a TSS
Position
of LDT In TSS
T I
end RPL f1 e I d
Pass from the power-up addresl to the mode Iwltch code.
The containing thll code must be at address FFFEIOH
.to place JMP Inltructlon phySical FFFFFOH. Jhe base
chosen t. the size of this segment.
cs_offlet
legment er
equ
org
jmp
OFEIOH Low 16 bits of starting address
OFFFOH-cs_offset; Start at addresl FFFFFOH
Do not change CS!
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Intel 80287 Specifications

General

Brand	Intel
Model	80287
Category	Computer Hardware
Language	English