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SINGLE
COMPONENT
SYSTEM
+5V
RESET
O------------~--~
+5V---....,
TEST 0
---
BUS
AND
PROG
CAN
BE
DRIVEN
ONLY
DURING
THIS
TIME-I
1--------
o
+23V
EA
+5V
____
---I
BUS
(
ADDRESS
AO-A7
X
DATA
>
<
DATA
OUT
PREVIOUS
X
ADDRESS
A8-A9
ADDRESS
P20·21
+25V
VDD
+5V-----------------------------------------I
+23V I
FLOAT
PROG
+OV
- -
--
,'--
____________________________
---1
FLOAT
'--
__
--i' - -
--
- - -
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.
PROGRAMMINGIVERIFY. SEQUENCE
8748 Erasure Characteristics
The erasure characteristics
of
the 8748 are
such that erasure begins to
occur
when
exposed
to
light
with wavelengths
sh<6rter
than approximately 4000 Angstroms (Al. It
should be noted
that
sunlight
and certain
types
of
fluorescent lamRs 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.
2-17
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
tAl. 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
12000jlW/cm
2
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.