Notes
(Cont'd)
Addressing
4.
The
SS
MOVE
instructions in the 70/45 (to maintain compatibility
with
the
System/360)
are
implemented such
that
if
the
source
and
destination fields
are
adjacent
(overlap each
other),
the
first
byte
of
the source field will be extended into
the
destination field,
resulting
in
a symbol
fill.
Similarly,
in
SS logical
instructions
with
adjacent
fields, each
byte
operation uses
the
result
of
the
preceding logical
operation
as
an
operand. Since
the
implementation
of
these
instruc-
tions in
the
70/46
are
more
complex,
the
purpose
of
this
note
(with
its
supporting
tables) is to define
this
implementation
in
further
detail.
The step-by-step operations
for
overlapped
and
non-overlapped fields
in
the
move
instructions
are
detailed
in
table
2A.
Similar
results·
are
obtained
for
the
SS Logicals except
that
instead
of
extending
a source
character
when fields overlap,
the
result
of
each operation is extended.
The conditions which determine
whether
a MOVE
in
the
70/46
will
result
in
an
actual move
or
in
a
fill
are
detailed on
the
chart
in
table
2B.
The
same rules apply to SS Logical
instructions
in
as
much
as
an
actual move is equivalent to a valid logical
result
and
a fill is
equivalent to
extending
the
preceding
result
as
an
operand. The
chart
may
generally be summarized
in
narrative
form
as
follows:
a. Two addresses
are
virtually
non-adjacent
and
they
do
not
trans-
late
into
the
same
page:
A move field results.
b.
Two addresses
are
virtually
adjacent
(page
and
displacement)
and
they
are:
(1)
in
the
same
segment:
a symbol
fill
results.
(2)
in
different segments
and
actual
addresses
are
adjacent:
a
symbol
fill
results.
(3)
in
different segments
and
actual
addresses
are
not
adjacent:
a field move results.
c.
If
one
address
is direct
(untranslated)
and
the
other
address
is a
virtual
address,
the
result
is a field move.
An
exception occurs
when
the
virtual
and
direct addresses
are
adjacent
and
the
trans-
lated
virtual
address
is
adjacent
to
the
direct
address,
in
which
case
the
result
is a symbol fill.
14
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