Hitachi MB-6890, Service Manual

Page: 77 / 123

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6-9-2 system
expansion
interface
block
In
level
master
3,
the
memory
expansion connectors
is
incorporated
which
enable
user
to
expand dynamic RAM
memory
and also
expansion connectors
are
used
for the
additional peripherals
and for
easy
expansion
of
the
WVU
power.
Following
is the
explanation of
the
system
expansion
interface block.
M U address
bus and data bus
are
connected to
general
expansion connectors
(I/F-l-I/F-6) and the address
decode
signal ROM-KIL to
control
the inside
main unit
is
outputted
from
system
expansion PCB.
MPU data bus, RAM
address
and expansion
memory
address
area
signals
are
connected to
memory
expansion
connectors (RAM3,
RAM4)
The address decoder
Signal ROM-KIL
for
internal control
is outputted
from
RAM
expansion
card.
Further
more,
this
signal
is
outputted
as
address
decode
signal
EXROM-KIL
for
system
expansion PCB
control.
l.
Operation when
the
memory
is
expanded.
The
memory map,
in
case
that
one
RAM
expansion
card is added by
8K
Byte,
is shown
at Fig.
es-46 (b).
By
expanding
RAM,"L"level
ROM-KIL
signal is outputted
from
memory
expansion
terminal RAM3 at the address
$800-$9FFF.
Also,
ROM-KILO signal
inside the unit
becomes"H"level
and ROM IC2 becomes
non-operable
and instead of
that data buffer
IC6 becomes operable
then RAM expansion
PCB data
bus and the
one
in
MPU
can
be
connected.
On
the other hand, ROM-KIL
signal, outputted
from
memory
expansion
terminal
is
outputted
as
EXROM-KIL
signals
on
general
expansion
terminal.this
signal
becomes
H"level
at
the address $8000-$9FFF
and
limit the address
usable
area
in
general
expansion
terminal.
Fig. 6-46 (c)
shows the
memory map
in
case
2 RAM
expansion PCB
are
added
at
maximum
level.
ROMIC2-IC5 operation
are
limited
by
ROM-KIL signal
in
the
memory
expansion
terminal
RAM3,
RAM4
monitor
area
SFOOO-FEFF,
SFFFO-$FFFP becomes operable
in
ICS,
and becomes
non-operable
in BASIC
area
in IC2-ICS.
2.
The operation
in
case system
is expanded.
In
this
case
that
system
expansion PCB
is added to general
expansion
terminal,
system
expansion data bus
and the
one
in
MPU
is connected.
Address signal
in
use,
in
system
expansion PCB
from general
expansion
terminal,
is outputted
as
ROM-KIL
signal, low
level inside the
unit then ROM-KILO signal
becomes "H".
This
limit the operation
of
ROMIC2-ICS and makes
data buffer
IC6 operable only
in
address
area
which
is used in
system
expansion
PCB.
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