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SINGLE
COMPONENT
SYSTEM
BUS
AND
PROG CAN
BE
DRIVEN
ONLY
DURING
THIS TIME
<
ADDRESS A
-A
7
X
)
—
(
DATA OUT
PREVIOUS
ADDRESS
X
ADDRESS
Ag-Ag
V D D
Don
„
FLOAT
PROG
+
ov
— —
__
~V
FLOAT
SEE
8048/8748
DATA
SHEET (CHAPTER
6)
FOR
DETAIL TIMING
SPECIFICATIONS.
WARNING: An
attempt
to
program
a
mis-socketed
8748
will result in
severe
damage
to
the
part.
An
indication of
a
properly socketed
part
is
the
appearance
of the
ALE
clock output.
The
lack
of
this
clock
may
be used
to disable the
programmer.
PROGRAMMING/VERIFY
SEQUENCE
8748
Erasure
Characteristics
The
erasure
characteristics
of
the
8748
are
such
that
erasure begins
to
occur
when
exposed
to
light
with
wavelengths
shorter
than approximately
4000
Angstroms
(A).
It
should be noted
that
sunlight
and
certain
types
of
fluorescent
lamps have wave-
lengths
in
the
3000-4000A
range.
Data
show
that
constant
exposure
to
room
level
fluorescent
lighting
could erase
the
typical
8748
in
approximately
3 years while
it
would
take
approximately
1
week
to
cause
erasure
when
exposed
to direct sunlight.
If
the
8748
is
to
be
exposed
to
these types
of
lighting
conditions
for
extended
periods
of
time,
opaque
labels
are available
from
Intel
which should be
placed over the 8748
win-
dow
to
prevent unintentional erasure.
When
erased,
bits of
the
8748 Program
Memory
are
in
the
logic
"0"
state.
The recommended
erasure
procedure
for
the
8748
is
exposure
to
shortwave
ultra-
violet light
which
has
a
wavelength
of
2537
Angstroms
(A).
The
integrated
dose
(i.e.,
UV
intensity
X
exposure
time)
for
erasure
should be
a
minimum
of
15W-sec/cm2.
The
erasure time
with
this
dosage
is
approxi-
mately 15
to
20 minutes
using
an
ultraviolet
lamp
with a
12000/iW/cm2
power
rating.
The
8748 should be
placed
within
one
inch
from
the
lamp
tubes during
erasure.
Some
lamps have
a
filter
on
their
tubes
and
this
filter
should be
removed
before
erasure.
2-17
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