M27C512-45C データシートの表示（PDF） - STMicroelectronics

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M27C512-45C

512 Kbit (64Kb x8) UV EPROM and OTP EPROM

STMicroelectronics 

M27C512

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 M27C512. To activate the ES

mode, the programming equipment must force

11.5V to 12.5V on address line A9 of the

M27C512. 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 man-

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

identifier code. For the STMicroelectronics

M27C512, these two identifier bytes are given in

Table 4 and can be read-out on outputs Q7 to Q0.

ERASURE OPERATION (applies for UV EPROM)

The erasure characteristics of the M27C512 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

M27C512 in about 3 years, while it would take ap-

proximately 1 week to cause erasure when ex-

posed to direct sunlight. If the M27C512 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 M27C512 window to

prevent unintentional erasure. The recommended

erasure procedure for the M27C512 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 a minimum

of 15 W-sec/cm2. The erasure time with this dos-

age is approximately 15 to 20 minutes using an ul-

traviolet lamp with 12000 µW/cm2 power rating.

The M27C512 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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