2. System Instruction of 80386
1. Pointer Parameter
2. Address Descriptor Table
3. Co-Processor and Multiprocessing
4. Multi tasking
5. Input/output
6. Interrupt Control
2
4. ARPL (Adjust Requested Privilege
Level)
Adjust RPL field of the selector
Compare RPL field of two segment selector
Zero Flag Gets affected
RPL field is stored in bit 0 and 1 of each operand
Cannot be executed in REAL mode
4
5. LAR-Load Access Right
Load Access Right Byte
Load the Access right byte from the segment descriptor
Zero flag get affected
Loading occurs only if CPL,RPL less than DPL
5
6. LSL: Load Segment Limit
Load the segment Limit
LSL register, selector
If loading is successful Zero flag get affected
Cannot be executed in real mode
6
7. VERR/VERW verify segment for
Read/Write
Verify segment for reading or writing
Code/data segment tested
Zero flag get affected
Cannot be executed in real mode
7
9. LLDT : Load Local descriptor table
Load the source into segment selector field of
Local Descriptor Table
The source is 16-bit register or memory location
NO SC,ES,SS,FS,CS and GS affected
No flags affected
This instruction Not executed in real mode
9
10. SLDT-Store Local Descriptor Table
Register
Store Local Descriptor Table Register
This instruction sore the segment selector from
LDTR into the specified memory Location or
Register
Zero flag get affected
Cannot be executed in real mode
10
11. LGDT-Load Global Descriptor Table
Register
This instruction loads the values from the source to the
GDTR
The source is 6 byte memory location
LGDT is the only instruction that directly load linear
address
No flags affected
This instruction executed in real mode
11
12. SGDT-Store Global Descriptor Table
Register
This instruction stores the values from the source to the
GDTR
The source is 6 byte memory location
LGDT is the only instruction that directly load linear
address
No flags affected
This instruction executed in real mode
12
14. CLTS: Clear Task Switch Flag
This Instruction used to clear the task Switch flag in CR0
It is Privilege instruction
Executed in real mode to allow initialization of protected mode
No flags affected
14
15. ESC: Escape to External Processor
It is used to pass the instruction to external co-processor
No flags affected
15
16. LOCK: Lock Bus
Lock Bus during next instruction
No flags Affected
16
18. LTR: Load Task Register
Load task register from source
Source can be 16 bit register or Memory location
LTR CX
18
19. STR: Store Task Register
Store task register at destination
Destination can be 16 bit register or Memory location
STR CX
Not executed in real mode
19