M27W401

Device description

11/23

M27W401, these two identifier bytes are given in Table 3 and can be read-out on outputs Q7

to Q0. Note that the M27W401 and M27C4001 have the same identifier bytes.

2.10

Erasure operation (applies to UV EPROM)

The erasure characteristics of the M27W401 are 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. Data shows that constant exposure to room level fluorescent lighting could erase a

typical M27W401 in about 3 years, while it would take approximately 1 week to cause

erasure when exposed to direct sunlight. If the M27W401 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 M27W401 window to prevent unintentional erasure. The recommended erasure

procedure for the M27W401 is exposure to short wave ultraviolet light which has wavelength

of 2537 Å. The integrated dose (i.e. UV intensity x exposure time) for erasure should be a

minutes using an ultraviolet lamp with 12000

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

00

10

00

00

20h

Device Code

01

00

00

01

41h