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M27256-F1 View Datasheet(PDF) - STMicroelectronics

Part Name
Description
Manufacturer
M27256-F1
ST-Microelectronics
STMicroelectronics ST-Microelectronics
M27256-F1 Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
M27256
DEVICE OPERATION (cont’d)
VIH), and VPP = 12.5V. The outputs will be in a Hi-z
state according to the signal presented to G. There-
fore, all devices with VPP = 12.5V and G = VIL will
present data on the bus independent of the E state.
When parallel programming several devices which
share the common bus, VPP should be lowered to
VCC (6V) and the normal read mode used to exe-
cute a program verify.
Electronic Signature
The Electronic Signature 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 for the
purpose of automatically matching the device to be
programmed with its corresponding programming
algorithm. This mode is functional in the 25°C ± 5°C
ambient temperature range that is required when
programming the M27256. To activate this mode,
the programming equipment must force 11.5V to
12.5V on address line A9 of the M27256. Two
identifier bytes may then be sequenced from the
device outputs by toggling address line A0 from VIL
to VIH. All other address lines must be held at VIL
during Electronic Signature mode. Byte 0 (A0 = VIL)
represents the manufacturer code and byte 1 (A0
= VIH) the device identifier code. For the STMi-
croelectronics M27256, these two identifier bytes are
given below.
ERASURE OPERATION (applies to UV EPROM)
The erasure characteristic of the M27256 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 M27256 in about 3 years, while it
would take approximately 1 week to cause erasure
when exposed to direct sunlight. If the M27256 is
to be exposed to these types of lighting conditions
for extended periods of time, it is suggested that
opaque lables be put over the M27256 window to
prevent unintentional erasure. The recommended
erasure procedure for the M27256 is exposure to
short wave ultraviolet light which has wavelength
2537 Å. The integrated dose (i.e. UV intensity x
exposure time) for erasure should be a minimum
of 15 W-sec/cm2. The erasure time with this dosage
is approximately 15 to 20 minutes using an ultra-
violet lamp with 12000 µW/cm2 power rating. The
M27256 should be placed within 2.5cm (1 inch) of
the lamp tubes during the erasure. Some lamps
have a filter on their tubes which should be re-
moved before erasure.
ORDERING INFORMATION SCHEME
Example:
M27256
-1 F 1
Speed and VCC Tolerance
-1
170 ns, 5V ±5%
-2
200 ns, 5V ±5%
blank 250 ns, 5V ±5%
-3
300 ns, 5V ±5%
-4
400 ns, 5V ±5%
-20
200 ns, 5V ±10%
-25
250 ns, 5V ±10%
Package
F
FDIP28W
Temperature Range
1 0 to 70 °C
6 –40 to 85 °C
For a list of available options (Speed, VCC Tolerance, Package, etc) refer to the current Memory Shortform
catalogue.
For further information on any aspect of this device, please contact STMicroelectronics Sales Office nearest
to you.
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