Owner`s manual
A3.3 EMS I/O Port Address Selections
EMS
uses 110 ports
to
set
up
mapping
information.
These
1/0
ports
are
selectable
and
a
number
of
110
ports
have
been
reserved
for
EMS
memory.
These
ports are:
Mapping
Registers
02X8:
42X8:
82X8:
C2X8:
page 1
page 2
page 3
page 4
Page
Frame
Registers
02X9
42X9
82X9
where
the
variable X is selectable
in
a
range
from
0
to
E.
The
page
frame
registers
determine
the
starting
address
of
the
EMS
window in
the
CPU
addressing space, while
the
mapping
registers
determine
which
16K page
of
physical
memory
of
the
EMS
board
is
to
be
mapped
into
the
window.
Each
RAM
3000 Deluxe has
four
16K pages
that
map
into
the
64K window, yet
at
anyone
time
there
should
not
be
more
than
one
active page
in
the
same page location
within
the
window. By
controlling
the
MSB
of
the
mapping
regis-
ter,
one
can
enable
or
disable
the
corresponding
page.
As
a
result,
more
than
one
EMS
card
can
be
used.
According
to
specification, EMS
can
support
up
to
8MB
of
memory.
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