M27V160

Device description

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2.9

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

ambient temperature range that is required when programming the M27V160. To activate

the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of

Two identifier bytes may then be sequenced from the device outputs by toggling address line

mode.

identifier code. For the STMicroelectronics M27V160, these two identifier bytes are given in

Table 3 and can be read-out on outputs Q7 to Q0. Note that the M27V160 and M27C160

have the same identifier bytes.

2.10

Erasure operation (applies to UV EPROM)

The erasure characteristics of the M27V160 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 M27V160 in about 3 years, while it would take approximately 1 week to

cause erasure when exposed to direct sunlight. If the M27V160 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 M27V160 window to prevent unintentional erasure. The recommended

erasure procedure for M27V160 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

Q15

and

Q7

Q14

and

Q6

Q13

and

Q5

Q12

and

Q4

Q11

and

Q3

Q10

and

Q2

Q9

and

Q1

Q8

and

Q0

Hex

Data

Manufacturer’s Code

001

000

00

20h

Device Code

101

100

01

B1h