M27C4001

Device operation

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2.10

Erasure operation (applies to UV EPROM)

The erasure characteristics of the M27C4001 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 M27C4001 in about 3 years, while it would take approximately 1 week to cause

erasure when exposed to direct sunlight. If the M27C4001 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 M27C4001 window to prevent unintentional erasure. The recommended erasure

procedure for the M27C4001 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

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.

Table 2.

1.

Mode

E

G

A9

Q7 - Q0

Read

Data Out

Output Disable

Hi-Z

Program

Data In

Verify

Data Out

Program Inhibit

Hi-Z

Standby

XX

Hi-Z

Electronic Signature

Codes

Table 3.

Electronic Signature

Identifier

A0

Q7

Q6

Q5

Q4

Q3

Q2

Q1

Q0

Hex Data

Manufacturer’s

Code

0

010

00

00

20h

Electronic

Signature

0

100

00

01

41h