LFS - Load Far Pointer Instruction

The LFS instruction is used to load (read) a segment and address from memory into registers.
The memory address most hold the Segment and offset address.

This command has 3 parts, Instruction, Register, and a 32 bit memory address made up of 16 bit Segment number followed by an offset from the start of it.

LFS loads the Segment first in to the FS Register, then loads the Offset address into the Register provided in the first operand.

Breakdown Description 16 bit Machine
Code

LFS ; Instruction 0F B4

SI ; Register number

[BX] ; A memory address from [BX]
; pointed to by BX

DataAddress ; A Label address 25 C0

LFS using a memory address

Assembly
Sample Description

MOV BX, 0x0345 ; Assign the memory address of the Pointer

or

MOV BX, DataAddress ; Assign the memory address of the Pointer

LFS SI, [BX] ; Call LFS

Alternate method

Assembly
Sample Description

MOV BX, 0x0005 ; Assign the memory address of the Pointer

PUSH BX

POP FS

MOV SI, DataAddress ; Assign the memory address of the Pointer
; to a Register

Assembly
Sample Description 16 bit Machine
Code

LFS SI, [BX] ; Load FS and a Register from
; the memory adress in [BX] 0F B4 33

Breakdown	Description	16 bit Machine Code
LFS	; Instruction	0F B4
SI	; Register number
[BX]	; A memory address from [BX] ; pointed to by BX
DataAddress	; A Label address	25 C0

Assembly Sample	Description
MOV BX, 0x0345	; Assign the memory address of the Pointer
or
MOV BX, DataAddress	; Assign the memory address of the Pointer
LFS SI, [BX]	; Call LFS

Assembly Sample	Description
MOV BX, 0x0005	; Assign the memory address of the Pointer
PUSH BX
POP FS
MOV SI, DataAddress	; Assign the memory address of the Pointer ; to a Register