42
The 68000's Instruction Set
Application:
NOP
s can be used to introduce a
delay
in code. Some programmers
use them to provide space for
patches
two or more
NOP
s can
later be replaced by branch or jump instructions to fix a bug. This
use of the
NOP
is seriously frowned upon, as errors should be
corrected by re-assembling the code rather than by patching it.
Condition codes:
X N Z V C
- - - - -
NOT
Logical complement
Operation:
[destination]
←
[destination]
Syntax:
NOT <ea>
Attributes:
Size = byte, word, longword
Description:
Calculate the logical complement of the destination and store the
result in the destination. The difference between
NOT
and
NEG
is
that
NOT
performs a bit-by-bit logical complementation, while a
NEG
performs a twos complement arithmetic subtraction. More-
over,
NEG
updates all bits of the CCR, while
NOT
clears the V- and
C-bits, updates the N- and Z-bits, and doesn't affect the X-bit.
Condition codes:
X N Z V C
- * * 0 0
Source operand addressing modes
OR
OR logical
Operation:
[destination]
←
[source] + [destination]
Syntax:
OR <ea>,Dn
OR Dn,<ea>
Attributes:
Size = byte, word, longword
Содержание 68000
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