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[STEP
1]
Sound
Output and
LED
Lamps
•
When
the
power
is
switched
on,
a continuous
tone
is
generated
by
the
PSG
(and continues
until
the
title
is
displayed).
• The
DO
thru
D7 LED
pattern changes
as
shown
in
the
accompanying
diagram each time
the
CENTRONICS
CHECK BOARD
STEP
button
is
pressed.
/•
LED-on
\Q
LED-off
D7
D6
D5 D4
D3
D2
D1
DO
[STEP
3]
PPI
Test
See
fig.
11-14
[STEP
4]
Ram
Test
•
The
RAM
test
is
executed with the
RAM
area
divided
into
four
parts.
First,
the
area
used
as
program
work
area
is
checked
by
tests
©
and
(6)
Table
11-1
(5)
8000-80FFH TEST
©
COOO-COFFH TEST
WORK
AREA ADDRESS
OK
OK
8000~80FFH
OK
NG
8000~80FFH
NG
OK
COOO—COFFH
NG
NG
CANT
CONTINUE
Fig.
11-11
Sound
output
and
LED
lamps
[STEP
2]
Title
Display
• When
the
STEP
button
is
pressed again
after
completing
STEP
1,
the
title
is
displayed
on
the
screen
(see
accompanying
diagram),
and
the
PSG
tone
is
stopped.
Operation of the
basic sections
and
the
CPU, PSG,
VDP,
and
PRINTER
PORT
statuses are
checked by
the
above
steps.
BORDER
COLOR
=
Cyan
PX-7
BACKGROUND
SELF TEST
COLOR
=
Blue
FOREGROUND
COLOR
= White
®
G
o
To
V-RAM TEST
Fig.
11-13
RAM
t(
Fig.
11-12
Title
display
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