MOVSX -- Move with Sign-Extend

Opcode     Instruction        Clocks   Description

0F  BE /r  MOVSX r16,r/m8     3/6      Move byte to word with sign-extend
0F  BE /r  MOVSX r32,r/m8     3/6      Move byte to dword, sign-extend
0F  BF /r  MOVSX r32,r/m16    3/6      Move word to dword, sign-extend

Operation

DEST := SignExtend(SRC);

Description

MOVSX reads the contents of the effective address or register as a byte or a word, sign-extends the value to the operand-size attribute of the instruction (16 or 32 bits), and stores the result in the destination register.

Flags Affected

None

Protected Mode Exceptions

#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH

Virtual 8086 Mode Exceptions

Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault

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