AMD Am186 Series, Instruction Set

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Instruction Set 4-139
LES LES
Examples
This example copies several of the characters in a string stored in memory to a series of
bytes in the same string that overlap the original characters. The microcontroller copies the
bytes, one by one, from last to first to avoid overwriting the source bytes.
Related Instructions
If you want to See
Load a full address stored in a doubleword into DS and another register LDS
Load the offset of a memory component into a register LEA
; defined in SEG_1 segment
STRING DB ”Am186EM*”,8 DUP (?); source and dest.
STRING_ADDR DD STRING ; full address of STRING
NUMCHARS EQU 8 ; copy eight characters
DELTA EQU 4 ; 4 bytes away
; direct assembler that DS and ES point to
; different segments of memory
ASSUME DS:SEG_1, ES:SEG_2
; set up DS and ES with different segment addresses
MOV AX,SEG_1 ; load one segment into DS
MOV DS,AX ; DS points to SEG_1
MOV AX,SEG_2 ; load another segment into ES
MOV ES,AX ; ES points to SEG_2
; load source offset (segment = DS)
; SIZE and TYPE are assembler directives
LEA SI, SIZE STRING - TYPE STRING
; load dest. segment (DS) into ES and offset into DI
LES DI,ES(SIZE STRING-TYPE STRING-DELTA)
MOV CX,NUMCHARS ; set up counter
STD ; process string high to low
; copy eight bytes of string to destination within string
REP MOVS STRING,ES:STRING