Program Verify

A verify should be performed on the programmed

bits to determine that they were correctly pro-

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 the25

°C ± 5°C ambient

temperature range that is required when program-

ming the M27128A.

To activate this mode, the programming equipment

must force 11.5V to 12.5V on address line A9 of the

M27128A. Two identifier bytes may then be se-

quenced from the device outputs by toggling ad-

code. For the SGS-THOMSON M27128A, these

two identifier bytes are given below.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristic of the M27128A 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 M27128A in about 3 years, while it

would take approximately 1 week to cause erasure

when exposed to direct sunlight. If the M27128A 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 M27128A window to

prevent unintentional erasure. The recommended

erasure procedure for the M27128A 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

is approximately 15 to 20 minutes using an ultra-

violet lamp with 12000

M27128A 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 re-

moved before erasure.

-2

200 ns, 5V

±5%

blank

250 ns, 5V

± 5%

-3

300 ns, 5V

± 5%

-4

450 ns, 5V

± 5%

-20

200 ns, 5V

± 10%

-25

250 ns, 5V

± 10%

-30

300 ns, 5V

± 10%

Package

F

FDIP28W

Temperature Range

1

0 to 70

°C

6

–40 to 85

°C

Example:

M27128A

-2

F

1

ORDERING INFORMATION SCHEME

catalogue.

For further information on any aspect of this device, please contact SGS-THOMSON Sales Office nearest

to you.

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M27128A