21-05-2012, 05:22 PM
Intel 8086 Instruction Set Overview
Intel 8086 Instruction Set Overview.ppt (Size: 1.91 MB / Downloads: 49)
Intel 8088 has ninety basic ( ie not counting addressing mode
variants) instructions
Instructions belong to one of the following groups: data
transfer, arithmetic, logic, string manipulation, control
transfer and processor control.
Instructions for moving strings
String instructions are repeated when prefixed by the REP mnemonic (CX contains the repetition count)
MOVS d,s - (MOVSB, MOVSW) memory to memory data transfer
LODS s - (LODSB and LODSW) copies data into AX or AH
STOS d - (STOSB, STOSW) stores data from AH or AX
Data movement using MOV
MOV d, s
d=destination (register or effective memory address),
s=source (immediate data, register or memory address)
MOV can transfer data from:
any register to any register (except CS register)
memory to any register (except CS)
immediate operand to any register (except CS)
any register to a memory location
immediate operand to memory
MOV cannot perform memory to memory transfers (must use a register as an intermediate storage).
MOV moves a word or byte depending on the operand bit-lengths; the source
and destination operands must have the same bit length.
MOV cannot be used to transfer data directly into the CS register.
Translate Instruction (XLAT)
Many applications need to quickly convert byte sized codes to other values mapping one byte value to another (e.g. mapping keyboard binary codes to ASCII code)
XLAT can perform a byte translation using a look-up table containing up to 256 elements
XLAT assumes that the 256-byte table starts at the address given by DS:BX (i.e. effective address formed by the DS and BX registers). AL is used as an index to point to the required element in the table prior to the execution of XLAT. The result of XLAT instruction is returned in the same register (AL).