at 12.5V, will program that M27C64A. A high level

E input inhibits the other M27C64A from being

programmed.

Program Verify

A verify (read) should be performed on the pro-

grammed bits to determine that they were correctly

programmed. The verify is accomplished with E

and G at VIL, P at VIH,VPP at 12.5V and VCC at 6V.

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 M27C64A. To activate this mode, the

programming equipmentmust force 11.5V to 12.5V

on address line A9 of the M27C64A, with

VPP=VCC=5V. Two identifier bytes may then be

sequenced from the device outputs by toggling

address 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 SGS-THOMSON M27C64A, these two identi-

fier bytes are given in Table 4 and can be read-out

on outputs Q0 to Q7.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristics of the M27C64A 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 wave-

lengths in the 3000-4000 Å range.

Research

shows that constant exposure to room level fluo-

rescent lighting could erase a typical M27C64A in

about 3 years, while it would take approximately 1

week to cause erasure when exposed to direct

sunlight. If the M27C64A 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 M27C64Awindow to prevent unintentional era-

sure. The recommended erasure procedure for

the M27C64A is exposure to short wave ultraviolet

light which has a wavelength of 2537 Å. The inte-

grated dose (i.e. UV intensity x exposure time) for

erasure should be a minimum of 15 W-sec/cm2.

The erasure time with this dosage is approximately

15 to 20 minutes using an ultraviolet lamp with

12000 uW/cm2 power rating. The M27C64A should

be placed within 2.5 cm (1 inch) of the lamp tubes

during the erasure. Some lamps have a filter on

their tubeswhich should be removed beforeerasure.

DEVICE OPERATIONS (cont’d)

Speed

-15

150 ns

-20

200 ns

-25

250 ns

-30

300 ns

Package

F

FDIP28W

C

PLCC32

Temperature Range

1

0 to 70

°C

6

–40 to 85

°C

Option

X

Additional

Burn-in

TR

Tape & Reel

Packing

Example:

M27C64A

-15 F

1 TR

ORDERING INFORMATION SCHEME

For a list of available options (Speed, Package, etc...) refer to the current Memory Shortform catalogue.

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

to you.

8/11

M27C64A