80C86 Datasheet, PDF (35/37 Pages) Intersil Corporation – CMOS 16-Bit Microprocessor

Instruction Set Summary (Continued)
MNEMONIC AND DESCRIPTION
STD = Set Direction
CLl = Clear Interrupt
ST = Set Interrupt
HLT = Halt
WAIT = Wait
ESC = Escape (to External Device)
LOCK = Bus Lock Prefix
NOTES:
AL = 8-bit accumulator
AX = 16-bit accumulator
CX = Count register
DS= Data segment
ES = Extra segment
Above/below refers to unsigned value.
Greater = more positive;
Less = less positive (more negative) signed values
if d = 1 then “to” reg; if d = 0 then “from” reg
if w = 1 then word instruction; if w = 0 then byte
instruction
if mod = 11 then r/m is treated as a REG field
if mod = 00 then DISP = O†, disp-low and disp-high
are absent
if mod = 01 then DISP = disp-low sign-extended
16-bits, disp-high is absent
if mod = 10 then DISP = disp-high:disp-low
if r/m = 000 then EA = (BX) + (SI) + DISP
if r/m = 001 then EA = (BX) + (DI) + DISP
if r/m = 010 then EA = (BP) + (SI) + DISP
if r/m = 011 then EA = (BP) + (DI) + DISP
if r/m = 100 then EA = (SI) + DISP
if r/m = 101 then EA = (DI) + DISP
if r/m = 110 then EA = (BP) + DISP †
if r/m = 111 then EA = (BX) + DISP
DISP follows 2nd byte of instruction (before data
if required)
† except if mod = 00 and r/m = 110 then
EA = disp-high: disp-low.
†† MOV CS, REG/MEMORY not allowed.
80C86
76543210
11111101
11111010
11111011
11110100
10011011
11011xxx
11110000
INSTRUCTION CODE
76543210
76543210
76543210
mod x x x r/m
if s:w = 01 then 16-bits of immediate data form the operand.
if s:w. = 11 then an immediate data byte is sign extended
to form the 16-bit operand.
if v = 0 then “count” = 1; if v = 1 then “count” in (C_L)
x = don't care
z is used for string primitives for comparison with ZF FLAG.
SEGMENT OVERRIDE PREFIX
001 reg 11 0
REG is assigned according to the following table:
16-BIT (w = 1)
8-BIT (w = 0)
SEGMENT
000 AX
000 AL
00 ES
001 CX
001 CL
01 CS
010 DX
010 DL
10 SS
011 BX
011 BL
11 DS
100 SP
100 AH
00 ES
101 BP
101 CH
00 ES
110 SI
110 DH
00 ES
111 DI
111 BH
00 ES
Instructions which reference the flag register file as a 16-bit object
use the symbol FLAGS to represent the file:
FLAGS =
X:X:X:X:(OF):(DF):(IF):(TF):(SF):(ZF):X:(AF):X:(PF):X:(CF)
Mnemonics © Intel, 1978
35
FN2957.3
January 9, 2009