M27W101

Device description

11/23

identifier code. For the STMicroelectronics M27W101, these two identifier bytes are given in

Table Table 3 and can be read-out on outputs Q7 to Q0.

Note that the M27W101 and M27C1001 have the same identifier byte.

2.10

Erasure operation (applies to UV EPROM)

The erasure characteristics of the M27W101 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 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 integrated dose (i.e. UV intensity x exposure time) for erasure

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’s Code

00100

000

20h

Device Code

00000

101

05h