M27C4002

Device operation

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M27C4002, these two identifier bytes are given in Table 3: Electronic Signature and can be

read-out on outputs Q7 to Q0.

2.10

Erasure operation (applies to UV EPROM)

The erasure characteristics of the M27C4002 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. Research shows that constant exposure to room level fluorescent lighting could

erase a typical M27C4002 in about 3 years, while it would take approximately 1 week to

cause erasure when exposed to direct sunlight. If the M27C4002 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 M27C4002 window to prevent unintentional erasure. The recommended

erasure procedure for the M27C4002 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 placed within 2.5cm (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

Q15-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.

1.

Outputs Q15-Q8 are set to '0'.

Identifier

A0

Q7

Q6

Q5

Q4

Q3

Q2

Q1

Q0

Hex Data

Manufacturer’s

Code

00100000

20h

Device Code

01000100

44h

Obsolete

Product(s)

- Obsolete

Product(s)