M87C257 STMICROELECTRONICS [STMicroelectronics], M87C257 Datasheet - Page 9

• Manufacturer Part Number: M87C257
• Description: ADDRESS LATCHED 256K 32K x 8 UV EPROM and OTP EPROM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Electronic Signature
The Electronic Signature (ES) mode allows the
reading out of a binary code from an EPROM that
will identify its manufacturer and type. This mode
is intended for use by programming equipment to
automatically match the device to be programmed
with its corresponding programming algorithm. The
ES mode is functional in the 25 C
temperature range that is required when program-
ming the M87C257.
To activate the ES mode, the programming equip-
ment must force 11.5V to 12.5V on address line A9
of the M87C257, with V
bytes may then be sequenced from the device
outputs by toggling address line A0 from V
All other address lines must be held at V
Electronic Signature mode. Byte 0 (A0=V
sents the manufacturer code and byte 1 (A0=V
the device identifier code. When A9 = V
not be toggled to latch each identifier address. For
the SGS-THOMSON M87C257, these two identi-
fier bytes are given in Table 4 and can be read-out
on outputs Q0 to Q7.
CC
= V
PP
= 5V. Two identifier
5 C ambient
ID
, AS need
IL
IL
IL
) repre-
to V
during
IH
IH
)
.
ERASURE OPERATION (applies for UV EPROM)
The erasure characteristics of the M87C257 is such
that erasure begins when the cells are exposed to
light with wavelengths shorter than approximately
4000 Å. It should be noted that sunlight and some
type of fluorescent lamps have wavelengths in the
3000-4000 Å range. Research shows that constant
exposure to room level fluorescent lighting could
erase a typical M87C257 in about 3 years, while it
would take approximately 1 week to cause erasure
when exposed to direct sunlight. If the M87C257 is
to be exposed to these types of lighting conditions
for extended periods of time, it is suggested that
opaque labels be put over the M87C257 window to
prevent unintentional erasure. The recommended
erasure procedure for the M87C257 is exposure to
short wave ultraviolet light which has wavelength
2537Å. The integrated dose (i.e. UV intensity x
exposure time) for erasure should be a minimum
of 15 W-sec/cm
age is approximately 15 to 20 minutes using an
ultraviolet lamp with 12000 W/cm
The M87C257 should be placed within 2.5 cm (1
inch) of the lamp tubes during the erasure. Some
lamps have a filter on their tubes which should be
removed before erasure.
2
. The erasure time with this dos-
2
power rating.
M87C257
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