Service manual
*
How
to
Use
RAM
Checker
Remove
monitor
ROM
from
the
socket
("M-ROM" marked on
the
PWB)
and insert
RAM
checker
into
the
socket
and
turn
on
the
power switch (the picture gets
"panic"
for
about
1 second):
then
the
following
RAM
TEST-1 and
RAM
TEST-2 will be automatically carried
out
from
the
address
$1000
to
the
maximum address
and
the
tested results will be displayed:
the
maximum
address refers
to
$5FFF
in
the
case
of
the
standard
set.
The
following
is
an
example
of
the
testing
performed
with
the
standard
set
(with RAMs being all normal).
Note:
RAM
(I) block, 16K bytes;
RAM
(11)
block, 4K bytes
RAM.
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.
RAM
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1) RAM
TEST-'
In
the
range from
the
address
$1000
to
the
maximum address,
data
$00
and
$FF
are subjected
to
auto-
matic write/read test;
if
error
is
caused,
"ER"
mark
is
indicated in
the
unit
of
4K
bytes.
In
the
above table,
3000-0K:
this means write/read
operation
has been normal from
the
address
$3000
to
$3F
FF.
6000-ER-6000-00,7F:
this means
there
exists
error
somewhere from
the
address
$6000
to
$6FFF;
this
error
is
because
the
standard set
is
provided with
up
to
$5FFF
but
with
no
more address, so it
doesn't
show a malfunction
of
RAM
itself.
An example showing an
error
really caused:
2OOO-ER·23&8.oo)~01·
]
An error
is
caused
in
the
addresses
$2000s;
namely, although
data
$00
has been
written
in
the
address
$235B, its read-out
data
is
$01.
2) RAM TEST-2
Write/read
test
is
carried
out
with
the
following data.
(a)
Write-in
data
$00
(from
the
address
$1000
to
the
maximum address)
(b) Write-in
data
$FF
(from
the
address
$1000
to
the
maximum address)
(c) Write-in
data
$00
(from
the
maximum
address
to
the
address
$1000)
(d) Write-in
data
$FF
(from
the
maximum address
to
the
address
$1000)
(e) Write-in
data
$FO and
$OF
to
be
entered
alternately (from
the
address
$1000
to
the
maximum
address and vice versa).
The above
table (RAM TEST-2) shows all
the
items
(a)
thru
(e) are normal -
the
indications
"00",
"FF",
"00",
"FF"
and
"FO"
correspond
to
(a)
thru
(e) respectively.
An example showing an error really caused:
FF
ER.-23FF..Q1
From
the
above, it can be seen
that
the
tests
(a)
and (b) are
both
normal and
that
although
data
$00
in
the
test
(c)
has been
written
in
the
address
$23F
F, its read-out
data
is
$01,
which means
that
an
error
has been caused.
In
this way, which
RAM
block
(I,ll
or
Ill)
has been subjected
to
the
error
is
first located, and
then
so does
which
RAM
component
having undergone
the
error, by
the
respective information given by
the
RAM
tester.
In
the
above example,
the
display
of
"$23FF"
means
RAM
(I) block
is
in
trouble,
and
the
display
of
read-out
data
"$01"
(with respect
to
write-in
data
"$00")
shows
RAM
1
of
the
block (I)
is
defective.
L-_~
_______
----------------------------------------------------'
-10-
11'
.'