M27C202 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M27C202 Datasheet PDF : 15 Pages
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M27C202
On-Board Programming
The M27C202 can be directly programmed in the
application circuit. See the relevant Application
Note AN620.
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 ± 5°C am-
bient temperature range that is required when pro-
gramming the M27C202. To activate the ES
mode, the programming equipment must force
11.5V to 12.5V on address line A9 of the M27C202
with VPP = VCC = 5V. Two identifier bytes may
then be sequenced from the device outputs by tog-
gling address line A0 from VIL to VIH. All other ad-
dress lines must be held at VIL during Electronic
Signature mode. Byte 0 (A0 = VIL) represents the
manufacturer code and byte 1 (A0 = VIH) the de-
vice identifier code. For the STMicroelectronics
M27C202, these two identifier bytes are given in
Table 4 and can be read-out on outputs Q7 to Q0.
ERASURE OPERATION (applies to UV EPROM)
The erasure characteristics of the M27C202 is
such that erasure begins when the cells are ex-
posed to light with wavelengths shorter than ap-
proximately 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 fluo-
rescent lighting could erase a typical M27C202 in
about 3 years, while it would take approximately 1
week to cause erasure when exposed to direct
sunlight. If the M27C202 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 M27C202 window to prevent unintentional era-
sure. The recommended erasure procedure for
the M27C202 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 era-
sure time with this dosage is approximately 15 to
20 minutes using an ultraviolet lamp with
12000µW/cm2 power rating. The M27C202 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 era-
sure.
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