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M27W101

On-Board Programming

The M27W101 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 M27W101. To activate the ES

mode, the programming equipment must force

11.5V to 12.5V on address line A9 of the

bytes may then be sequenced from the device out-

Electronic Signature mode.

code. For the STMicroelectronics M27W101,

these two identifier bytes are given in Table 4 and

can be read-out on outputs Q7 to Q0.

Note that the M27W101 and M27C1001 have the

same identifier byte.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristics of the M27W101 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 M27W101 in

about 3 years, while it would take approximately 1

week to cause erasure when exposed to direct

sunlight. If the M27W101 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 M27W101 window to prevent unintentional

erasure. The recommended erasure procedure for

the M27W101 is exposure to short wave ultraviolet

light which has a wavelength of 2537 Å. The inte-

grated dose (i.e. UV intensity x exposure time) for

erasure should be a minimum of 15 W-sec/cm

The erasure time with this dosage is approximate-

ly 15 to 20 minutes using an ultraviolet lamp with

12000

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.