M27W801 datasheet(10/16 Pages) STMICROELECTRONICS

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M27W801

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On-Board Programming

The M27W801 can be directly programmed in the

application circuit. See the relevant Application

Note AN620.

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 am-

bient temperature range that is required when pro-

gramming the M27W801. To activate the ES

mode, the programming equipment must force

11.5V to 12.5V on address line A9 of the

M27W801. Two identifier bytes may then be se-

quenced from the device outputs by toggling ad-

dress line A0 from VIL to VIH. All other address

lines must be held at VIL during Electronic Signa-

ture mode.

Byte 0 (A0 = VIL) represents the manufacturer

code and byte 1 (A0 = VIH) the device identifier

code. For the STMicroelectronics M27W801,

these two identifier bytes are given in Table 4 and

can be read-out on outputs Q7 to Q0.

Note that the M27W801 and M27C801 have the

same identifier byte.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristics of the M27W801 is

such that erasure begins when the cells are ex-

posed to light with wavelengths shorter than ap-

proximately 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

M27W801 in about 3 years, while it would take ap-

proximately 1 week to cause erasure when ex-

posed to direct sunlight. If the M27W801 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 M27W801 window

to prevent unintentional erasure. The recommend-

ed erasure procedure for the M27W801 is expo-

sure to short wave ultraviolet light which has

wavelength 2537 Å. The integrated dose (i.e. UV

intensity x exposure time) for erasure should be a

minimum of 30 W-sec/cm2. The erasure time with

this dosage is approximately 30 to 40 minutes us-

ing an ultraviolet lamp with 12000

µW/cm2 power

rating. The M27W801 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.

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