M27C801 Device description
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the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of
the M27C801. Two identifier bytes may then be sequenced from the device outputs by
toggling address line A0 from V
IL
to V
IH
. All other address lines must be held at V
IL
during
Electronic Signature mode. Byte 0 (A0 = V
IL
) represents the manufacturer code and byte 1
(A0 = V
IH
) the device identifier code. For the STMicroelectronics M27C801, these two
identifier bytes are given in Ta bl e 3 and can be read-out on outputs Q7 to Q0.
2.10 Erasure operation (applies to UV EPROM)
The erasure characteristics of the M27C801 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 M27C801 in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M27C801 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 M27C801 window to prevent unintentional erasure. The recommended
erasure procedure for the M27C801 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 30 W-sec/cm
2
. The erasure time with this dosage is approximately
30 to 40 minutes using an ultraviolet lamp with 12000 µW/cm
2
power rating. The M27C801
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.
Table 3. Electronic signature
Identifier A0 Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 Hex Data
Manufacturer code V
IL
00100000 20h
Device code V
IH
01000010 42h
Obsolete Product(s) - Obsolete Product(s)
