TI486 Microprocessor - Al Kossow's Bitsavers

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Table 7-17. Instructions, Opcodes, Flags, and Clock Summary (Continued)
FLAGS
REAL MODE
CLOCKS
INSTRUCTION OPCODE
0 D I T S Z A P C
REGI
CACHE
REG!
F F F F F F F F F
CACHE
CACHE
HIT
MISS
HIT
LAHF Load AH with Flags 9F u u u u u u u u u 2 2
PROTECTED
MODE CLOCKS
NOTES
CACHE READ PROTECTED
MISS MODE MODE
LAR Load Access Rights u u u u u m u u u 3 2,S,6,12
From RegisterlMemory OF 02[mod reg rIm] 11/12 14
LDS Load Pointer to OS CS [mod reg rIm] u u u u u u u u u 6 7 23 24 1 2,6,13
LEA Load Effective Address 80 [mod reg rIm] u u u u u u u u u
No Index Register 2 2
With Index Register 3 3
LEAVE Leave Current Stack Frame C9 u u u u u u u u u 3 4 3 4 1 2
LES Load Pointer to ES C4 [mod reg rIm] u u u u u u u u u 6 7 23 24 1 2,6,13
LFS Load Pointer to FS OF 84[mod reg rIm] u u u u u u u u u 6 7 23 24 1 2,6,13
LGDT Load GOT Register OF 01 [mod 010 rIm] u u u u u u u u u 9 9 9 9 1,10 2,11
LGS Load Pointer to GS OF 8S[mod reg rIm] u u u u u u u u u 6 7 23 24 1 2,6,13
LlDT Load lOT Register OF 01 [mod 011 rIm] u u u u u u u u u 9 9 9 9 1,10 2,11
LLDT Load LOT Register u u u u u u u u u 3 2,S,6,11
From RegisterlMemory OF OO[mod 010 rIm] 16/17 18
LMSW Load Machine Status Word u u u u u u u u u 1,10 2,11
From RegisterlMemory OF 01 [mod 110 rIm] S 8 S 8
LODS Load String A [110w] u u u u u u u u u 4 4 4 4 1 2
LOOP Offset Loop/No Loop E2:J: u u u u u u u u u 714 913 8
t = immediate data + = 8-bit displacement § = 16-bit displacement 11 = 32-bit displacement m = Flag modified u = Flag unchanged
Notes:
1) Exception 13 fault (general protection) will occur in Read Mode if an operand reference is made that partially or fully extends beyond the maximum CS, OS, ES, FS, or GS segment
limit (FFFFh). Exception 12 fault (stack segment limit violation or not present) will occur in Real Mode if an operand reference is made that partially or fully extends beyond the
maximum SS limit.
2) Exception 13 fault will occur if the memory operand in CS, OS, ES, FS, or GS cannot be used due to either a segment limit violation or an access rights violation. If a stack limit
is violated, an exception 12 occurs.
3) This is a Protected Mode instruction. Attempted execution in Real Mode will result in exception 6 (invalid opcode).
4) An exception may occur, depending on the value of the operand.
S) LOCK is asserted during descriptor table accesses. __
6) All segment descriptor accesses in the GOT or LOT made by this instruction will automatically assert LOCK to maintain descriptor integrity in multiprocessor systems.
7) JMP, CALL, INT, RET, and IRET instructions referring to another code segment will cause an exception 13, if an applicable privilege rule is violated.
8) The destination of a JMP, CALL, INT, RET, or IRET must be in the defined limit of a code segment or an exception 13 fault will occur.
9) An exception 13 fault occurs if CPL is greater than IOPL.
1 O)This instruction may be executed in Real Mode. in Real Mode, its purpose is primarily to initialize the CPU for Protected Mode.
11) An exception 13 fault occurs if CPL is greater than 0 (0 is the most privileged level).
12)Any violation of privilege rules as apply to the selector operand does not cause a Protection exception, rather, the zero flag is cleared.
13)For segment load operations, the CPL, RPL, and OPL must agree witht he privolege rules to avoid an exception 13 fault. The segment's descriptor must indicate "presenf' or
exception 11 (OS, OS, ES, FS, GS not present). If the SS register is loaded and a stack segment not present is detected, and exception 12 occurs.
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