A386DX Ver la hoja de datos (PDF) - Intel
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A386DX Datasheet PDF : 139 Pages
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Intel386TM DX MICROPROCESSOR
Register
General Registers
Segment Registers
Flag Register
Control Registers
GDTR
IDTR
LDTR
TR
Debug Control
Test Registers
Table 2-1 Register Usage
Use in
Real Mode
Use in
Protected Mode
Load
Store
Load
Store
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
PL e 0
PL e 0
Yes
Yes
PL e 0
Yes
Yes
Yes
PL e 0
Yes
No
No
PL e 0
Yes
No
No
PL e 0
Yes
Yes
Yes
PL e 0
PL e 0
Yes
Yes
PL e 0
PL e 0
Use in
Virtual 8086 Mode
Load
Store
Yes
Yes
Yes
Yes
IOPL
IOPL
No
Yes
No
Yes
No
Yes
No
No
No
No
No
No
No
No
NOTES
PL e 0 The registers can be accessed only when the current privilege level is zero
IOPL The PUSHF and POPF instructions are made I O Privilege Level sensitive in Virtual 8086 Mode
5) However registers which have been previ-
ously stored may be reloaded without mask-
ing
Depending upon the values of undefined regis-
ter bits will make your software dependent upon
the unspecified Intel386 DX handling of these
bits Depending on undefined values risks mak-
ing your software incompatible with future proc-
essors that define usages for the Intel386 DX-
undefined bits AVOID ANY SOFTWARE DEPEN-
DENCE UPON THE STATE OF UNDEFINED In-
tel386 DX REGISTER BITS
2 4 INSTRUCTION SET
2 4 1 Instruction Set Overview
The instruction set is divided into nine categories of
operations
Data Transfer
Arithmetic
Shift Rotate
String Manipulation
Bit Manipulation
Control Transfer
High Level Language Support
Operating System Support
Processor Control
These Intel386 DX instructions are listed in Table
2-2
All Intel386 DX instructions operate on either 0 1 2
or 3 operands where an operand resides in a regis-
ter in the instruction itself or in memory Most zero
operand instructions (e g CLI STI) take only one
byte One operand instructions generally are two
bytes long The average instruction is 3 2 bytes long
Since the Intel386 DX has a 16-byte instruction
queue an average of 5 instructions will be pre-
fetched The use of two operands permits the follow-
ing types of common instructions
Register to Register
Memory to Register
Immediate to Register
Register to Memory
Immediate to Memory
The operands can be either 8 16 or 32 bits long As
a general rule when executing code written for the
Intel386 DX (32-bit code) operands are 8 or 32 bits
when executing existing 80286 or 8086 code (16-bit
code) operands are 8 or 16 bits Prefixes can be
added to all instructions which override the default
length of the operands (i e use 32-bit operands for
16-bit code or 16-bit operands for 32-bit code)
For a more elaborate description of the instruction
set refer to the Intel386 DX Programmer’s Refer-
ence Manual
15
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