Pioneer PX-7 Service Manual page 61

PX-7
• The
RAM
used
in
the
PX-7
consists
of four
16K
X
4-bit
D-RAMs
to
provide
32K
bytes of
RAM
area
from 8000
to
FFFFH.
•
These
four
D-RAMs
are allocated in
the
follow-
ing
way.
IC18
1C
1
6
IC19
8000
thru
BFFFH
C000
thru
FFFFH
• That
is,
the
RAM
area
8000
thru
BFFFH
is
formed by
the IC15/IC18
pair,
and
the
C000
thru
FFFFH
area
is
formed by
the
IC16/IC19
pair.
•
A work
area can thus be
secured as long as
one
of the above
pairs
is
operating.
®
If
both
pairs
are
NG,
however, subsequent
tests
cannot be
executed.
The CAN'T
CONTINUE
message appears
on
the
screen,
an accompanying
tone
is
generated,
and
the program
is
halted.
Rather than
a defect
in
the
RAM
itself,
NG
condi-
tions are usually
due
to a
failure in the access
stage.
Ther
e fore,
when
checking
the
circuitry,
check
that
RAS, CAS, WE, OE,
ADDRESS
LINE, and
DATA
LINE
are
all
normal.
An
accessing
failure
will
certainly
be the
most
likely
cause
if
the
CAN'T
CONTINUE
condition
occurs.
(WORK
AREA
TEST)
61
Fig.
1
1-15
Work
area
test
flow
chart