up: Chapter 17 -- 80386 Instruction Set
prev: NOT One's Complement Negation
next: OUT Output to Port

OR -- Logical Inclusive OR

Opcode       Instruction       Clocks    Description

0C  ib       OR AL,imm8        2         OR immediate byte to AL
0D  iw       OR AX,imm16       2         OR immediate word to AX
0D  id       OR EAX,imm32      2         OR immediate dword to EAX
80  /1 ib    OR r/m8,imm8      2/7       OR immediate byte to r/m byte
81  /1 iw    OR r/m16,imm16    2/7       OR immediate word to r/m word
81  /1 id    OR r/m32,imm32    2/7       OR immediate dword to r/m dword
83  /1 ib    OR r/m16,imm8     2/7       OR sign-extended immediate byte
                                         with r/m word
83  /1 ib    OR r/m32,imm8     2/7       OR sign-extended immediate byte
                                         with r/m dword
08  /r       OR r/m8,r8        2/6       OR byte register to r/m byte
09  /r       OR r/m16,r16      2/6       OR word register to r/m word
09  /r       OR r/m32,r32      2/6       OR dword register to r/m dword
0A  /r       OR r8,r/m8        2/7       OR byte register to r/m byte
0B  /r       OR r16,r/m16      2/7       OR word register to r/m word
0B  /r       OR r32,r/m32      2/7       OR dword register to r/m dword

Operation

DEST := DEST OR SRC;
CF := 0;
OF := 0

Description

OR computes the inclusive OR of its two operands and places the result in the first operand. Each bit of the result is 0 if both corresponding bits of the operands are 0; otherwise, each bit is 1.

Flags Affected

OF := 0, CF := 0; SF, ZF, and PF as described in Appendix C; AF is undefined

Protected Mode Exceptions

#GP(0) if the result is in a nonwritable segment; #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

up: Chapter 17 -- 80386 Instruction Set
prev: NOT One's Complement Negation
next: OUT Output to Port