376 datasheet(20/95 Pages) INTEL

20 / 95 page

376 EMBEDDED PROCESSOR

NAME FLAT

name of the object module

EXTRN

c startupnear

this is the label jmped to after init

pe flag

equ 1

data selc

equ 20h

assume code is GDT 3

data GDT 4

INIT CODE

SEGMENT ER PUBLIC USE32

Segment base at 0ffffff80h

PUBLIC GDT DESC

gdt desc

PUBLIC

START

start

cld

clear direction flag

smsw bx

check for processor (80376) at reset

test bl1

use SMSW rather than MOV for speed

jnz pestart

realstart

is an 80386 and in real mode

db 66h

force the next operand into 32-bit mode

mov eaxoffset gdt desc

move address of the GDT descriptor into eax

xor ebxebx

clear ebx

mov bhah

load 8 bits of address into bh

move blal

load 8 bits of address into bl

db 67h

db 66h

use the 32-bit form of LGDT to load

lgdt cs

ebx

the 32-bits of address into the GDTR

smsw ax

go into protected mode (set PE bit)

or alpe flag

lmsw ax

jmp next

flush prefetch queue

pestart

mov ebxoffset gdt desc

xor eaxeax

mov axbx

lower portion of address only

lgdt cs

eax

xor ebxebx

initialize data selectors

mov b1data selc

GDT 3

mov dsbx

mov ssbx

mov esbx

mov fsbx

mov gsbx

jmp pejump

xor ebxebx

initialize data selectors

mov b1data selc

GDT 3

mov dsbx

mov ssbx

mov esbx

mov fsbx

mov gsbx

db 66h

for the 80386

need to make a 32-bit jump

pejump

jmp far ptr c startup

but the 80376 is already 32-bit

org 70h

only if segment base is at 0ffffff80h

jmp short start

INIT CODE ENDS

END

376 Datasheet(PDF) 20 Page - Intel Corporation

376 Datasheet(HTML) 20 Page - Intel Corporation

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