M27C256B-45F6 Ver la hoja de datos (PDF) - STMicroelectronics
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M27C256B-45F6 Datasheet PDF : 24 Pages
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M27C256B
Device operation
2.10 Erasure operation (applies for UV EPROM)
The erasure characteristics of the M27C256B is such that erasure begins when the cells are
exposed to light with wavelengths shorter than approximately 4000 Ã…. It should be noted
that sunlight and some type of fluorescent lamps have wavelengths in the 3000-4000 Ã…
range. Research shows that constant exposure to room level fluorescent lighting could
erase a typical M27C256B in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M27C256B 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 M27C256B window to prevent unintentional erasure. The recommended
erasure procedure for the M27C256B is exposure to short wave ultraviolet light which has
wavelength 2537Ã…. 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 ultraviolet lamp with 12000 µW/cm2 power rating. The M27C256B
) should be placed within 2.5 cm (1 inch) of the lamp tubes during the erasure. Some lamps
t(s have a filter on their tubes which should be removed before erasure.
uc Table 2. Operating modes(1)
rod Mode
E
P Read
te Output Disable
le Program
so Verify
Ob Program Inhibit
- Standby
t(s) Electronic Signature
VIL
VIL
VIL Pulse
VIH
VIH
VIH
VIL
c 1. X = VIH or VIL, VID = 12V ± 0.5V.
du Table 3. Electronic signature
ro Identifier
A0 Q7 Q6
P Manufacturer’s
teCode
VIL
0
0
ObsoleDevice Code
VIH
1
0
G
VIL
VIH
VIH
VIL
VIH
X
VIL
Q5 Q4
1
0
0
0
A9
X
X
X
X
X
X
VID
Q3 Q2
0
0
1
1
VPP
Q7-Q0
VCC
Data Out
VCC
Hi-Z
VPP
Data In
VPP
Data Out
VPP
Hi-Z
VCC
Hi-Z
VCC
Codes
Q1 Q0 Hex Data
0
0
20h
0
1
8Dh
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