Intel MCS48 User Manual page 253

2708 FAMILY
A.
C. Characteristics
Symbol
Parameter
2708-1
Limits
Min. Typ. Max.
2708, 2708L, Limits
Min. Typ. Max.
Units
Ucc Address
to
Output
Delay 280 350 280 450
ns
tco
Chip
Select to
Output
Delay 60 120 60 120
ns
tDF
Chip
Deselect to
Output
Float
120
120
ns
tfJH
Address to
Output Hold
ns
CAPACITANCE
11
'
T A
= 25°C,
f
=
1
MH2
Symbol
Parameter Typ. Max.
Unit.
Conditions
C|N
Input Capacitance 4
6
pF
V|
N
=
ov
C
OUT
Output
Capacitance 8
12 PF
Vqut =
0V
A.C.
TEST CONDITIONS:
Output
Load:
1
TTL
gate
and
C
L
= 100 pF
Input
Rise
and
Fall
Times:
<20
ns
Timing Measurement
Reference Levels: 0.8V and
2.8V
for inputs; 0.8V and 2.4V
for outputs.
Input
Pulse Levels: 0.65V
to
3.0V
Note:
1.
This parameter
is
periodically sampled and
is
not
100%
tested.
Waveforms
x
DATA OUT INVALID
ERASURE
CHARACTERISTICS
form
Intel
which
should be placed over
the
2708 window
to prevent unintentional
erasure.
The
erasure
characteristics
of the 2708
family
are
such that
erasure begins to occur
when
exposed
to
light
with wave-
lengths shorter than approximately 4000
Angstroms
(A).
It
should be noted
that sunlight and
certain
types of
fluores-
cent lamps have wavelengths
in
the
3000— 4000A
range.
Data
show
that constant exposure
to
room
level fluores-
cent
lighting
could
erase the
typical
device
in
approxi-
mately
3 years, while
it
would
take approximately
1
week
to cause erasure
when
exposed
to direct
sunlight.
If
the
2708
is
to
be exposed
to these types of
lighting
conditions
for extended
periods of time, opaque
labels are available
The recommended
erasure procedure
(see
Data Catalog
PROM/ROM
Programming
Instructions Section)
for
the
2708
family
is
exposure
to
shortwave
ultraviolet
light
which has
a
wavelength
of
2537 Angstroms
(A).
The
inte-
grated
dose
(i.e.,
UV
intensity
X
exposure time) for erasure
should be
a
minimum
of
15 W-sec/cm
2
.
The
erasure time
with
this
dosage
is
approximately 15
to
20 minutes
using an
ultraviolet
lamp
with
a
12000 /iW/cm
2
power
rating.
The
device
should be
placed within
1
inch of the
lamp
tubes
during
erasure.
Some
lamps have
a
filter
on
their
tubes
which should be removed
before
erasure.
7-15