Specifications

MICROPROCESSADORES
CONJUNTO DE INSTRUÇÕES DO 8086
4
Luís Miguel Charrua Figueiredo 4 - 2 E.N.I.D.H.
Disables the maskable hardware interrupts by clearing the
Interrupt flag. NMI's and software interrupts are not
inhibited.
CMC - Complement Carry Flag
Usage: CMC
Modifies flags: CF
Toggles (inverts) the Carry Flag
CMP - Compare
Usage: CMP dest,src
Modifies flags: AF CF OF PF SF ZF
Subtracts source from destination and updates the flags
but does not save result. Flags can subsequently be
checked for conditions.
CMPS - Compare String (Byte, Word or Doubleword)
Usage: CMPS dest,src
CMPSB
CMPSW
Modifies flags: AF CF OF PF SF ZF
Subtracts destination value from source without saving
results. Updates flags based on the subtraction and the
index registers (E)SI and (E)DI are incremented or
decremented depending on the state of the Direction
Flag. CMPSB inc/decrements the index registers by
1, CMPSW inc/decrements by 2, while CMPSD
increments or decrements by 4. The REP prefixes can be
used to process entire data items.
CWD - Convert Word to Doubleword
Usage: CWD
Modifies flags: None
Extends sign of word in register AX throughout register
DX forming a doubleword quantity in DX:AX.
DAA - Decimal Adjust for Addition
Usage: DAA
Modifies flags: AF CF PF SF ZF (OF undefined)
Corrects result (in AL) of a previous BCD addition
operation. Contents of AL are changed to a pair of packed
decimal digits.
DAS - Decimal Adjust for Subtraction
Usage: DAS
Modifies flags: AF CF PF SF ZF (OF undefined)
Corrects result (in AL) of a previous BCD subtraction
operation. Contents of AL are changed to a pair of packed
decimal digits.
DEC - Decrement
Usage: DEC dest
Modifies flags: AF OF PF SF ZF
Unsigned binary subtraction of one from the destination.
DIV - Divide
Usage: DIV src
Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)
Unsigned binary division of accumulator by source. If the
source divisor is a byte value then AX is divided by "src"
and the quotient is placed in AL and the remainder in AH.
If source operand is a word value, then DX:AX is divided
by "src" and the quotient is stored in AX and the
remainder in DX.
ESC - Escape
Usage: ESC immed,src
Modifies flags: None
Provides access to the data bus for other resident
processors. The CPU treats it as a NOP but places
memory operand on bus.
HLT - Halt CPU
Usage: HLT
Modifies flags: None
Halts CPU until RESET line is activated, NMI or maskable
interrupt received. The CPU becomes dormant but
retains the current CS:IP for later restart.
IDIV - Signed Integer Division
Usage: IDIV src
Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)
Signed binary division of accumulator by source. If
source is a byte value, AX is divided by "src" and the
quotient is stored in AL and the remainder in AH. If
source is a word value, DX:AX is divided by "src", and the
quotient is stored in AL and the remainder in DX.
IMUL - Signed Multiply
Usage: IMUL src
Modifies flags: CF OF (AF,PF,SF,ZF undefined)