Instruction Set Summary
A-2
Table A-1
Variables Used In Instruction Set Summary Tables
Variable Function
Values Description
d
Specifies direction.
0
to
r/m
1
to
reg
data-8
data-low
data-high
data-SX
Specifies a non-address constant data used by the
instruction. The "8" indicates an 8-bit constant; "low",
the low-order byte of a 16-bit constant; "high", the
high order byte of a 16-bit constant; and "SX", an 8-
bit constant that is sign-extended for a 16-bit
operation.
disp-8
disp-low
disp-high
Specifies the displacement. The "8" indicates an 8-
bit displacement; "low", the low-order byte of a 16-bit
displacement; and "high", the high-order byte of a 16-
bit displacement. For some forms of MOV, specifies
a 0-relative address.
mod
Along with
r/m
, determines the effective address of
the memory operand.
11
r/m
is treated as a
reg
field
00
DISP = 0, disp-low and disp-high are absent
01
DISP = disp-low sign-extended to 16-bits, disp-high is absent
10
DISP = disp-high: disp-low
r/m
Along with
mod
, determines the effective address of
the memory operand.
000
EA = (BX)+(SI)+DISP
001
EA = (BX)+(DI)+DISP
010
EA = (BP)+(SI)+DISP
011
EA = (BP)+(DI)+DISP
100
EA = (SI)+DISP
101
EA = (DI)+ DISP
110
EA = (BP)+ DISP (except if mod=00, then EA = disp-high:disp:low)
111
EA = (BX)+DISP
reg
Represents a register, and is assigned according to
the value of
w
and
reg
.
000
AL, if w=0 or implicit 8-bit
AX, if w=1 or implicit 16-bit
001
CL, if w=0 or implicit 8-bit
CX, if w=1 or implicit 16-bit
010
DL, if w=0 or implicit 8-bit
DX, if w=1 or implicit 16-bit
011
BL, if w=0 or implicit 8-bit
BX, if w=1 or implicit 16-bit
100
AH, if w=0 or implicit 8-bit
SP, if w=1 or implicit 16-bit
101
CH, if w=0 or implicit 8-bit
BP, if w=1 or implicit 16-bit
110
DH, if w=0 or implicit 8-bit
SI, if w=1 or implicit 16-bit
111
BH, if w=0 or implicit 8-bit
DI, if w=1 or implicit 16-bit
s
Specifies immediate operand sign-extension.
0
no sign extension
1
sign-extend (for 16-bit operations only, w=1)
seg-low
seg-high
Specifies the segment base address value.
Represents the high-order 16 bits of a 20-bit address,
with an implicit 4 low-order 0 bits.
sreg
Specifies a segment register.
00
ES register
01
CS register
10
SS register
11
DS register
w
Specifies an 8- or 16-bit value.
0
8-bit value
1
16-bit value
XXX YYY
Specifies opcode to proc. ext.
Notes:
1 – DISP follows the operand address (before data if required).
2 – The physical addresses of all operands addressed by the BP register are computed using the SS segment register. The physical addresses
of the destination operands of the string primitive operations (those addressed by the DI register) are computed using the ES segment, which
cannot be overridden.
Summary of Contents for Am186 Series
Page 1: ...Am186 and Am188 Family Instruction Set Manual February 1997...
Page 10: ...Table of Contents x...
Page 18: ...Programming 1 8...
Page 40: ...Instruction Set Listing 3 14...