Electronic Signature

The Electronic Signature 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.

This mode is functional in the 25

°C ± 5 °C ambient

temperature range that is required when program-

ming the M27512. To activate this mode, the pro-

gramming equipment must force 11.5V to 12.5V on

address line A9 of the M27512. Two identifier bytes

may then be sequenced from the device outputs by

Signature mode, except for A14 and A15 which

identifier code.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristic of the M27512 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 M27512 in about 3 years, while it

would take approximately 1 week to cause erasure

when expose to direct sunlight. If the M27512 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 M27512 window to

prevent unintentional erasure. The recommended

erasure procedure for the M27512 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

approximately 15 to 20 minutes using an ultraviolet

lamp with 12000

M27512 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 re-

moved before erasure.

-2

200 ns, 5V

±5%

blank

250 ns, 5V

±5%

-3

300 ns, 5V

±5%

-20

200 ns, 5V

±10%

-25

250 ns, 5V

±10%

Package

F

FDIP28W

Temperature Range

1

0 to 70

°C

6

–40 to 85

°C

Example:

M27512

-2

F

1

ORDERING INFORMATION SCHEME

catalogue.

For fur ther inform ation o n any aspect of this device, please cont act STMicroelectronics Sales Office nearest

to you.

M27512

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