
On-Board Programming
The M27C1001can be directlyprogrammed inthe
application circuit. See the relevant Application
NoteAN620.
Electronic Signature
The Electronic Signature (ES) mode allows the
reading out ofa binary code from an EPROM that
will identify its manufacturer and type. This mode
is intended for use by programming equipment to
automaticallymatch the device to be programmed
withitscorrespondingprogrammingalgorithm.The
ES mode is functionalin the 25°C±5°C ambient
temperaturerange that is requiredwhen program-
ming theM27C1001.To activatethe ES mode, the
programmingequipmentmustforce11.5Vto 12.5V
on address line A9 of the M27C1001, 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.
Byte0 (A0=VIL) representsthe manufacturercode
and byte1(A0=VIH) thedevice identifiercode. For
the SGS-THOMSON M27C1001, thesetwo identi-
fier bytes are given in Table4 andcan be read-out
on outputsQ0 to Q7.
ERASURE OPERATION (applies to UV EPROM)
The erasure characteristics of the M27C1001 is
such that erasure begins when the cells are ex-
posed to light with wavelengths shorter than ap-
proximately4000Å.Itshouldbenotedthatsunlight
and some type of fluorescent lamps have wave-
lengths in the 3000-4000 Å range. Research
shows that constant exposure to room level fluo-
rescentlighting could erase a typical M27C1001in
about3 years, while it wouldtake approximately1
week to cause erasure when exposed to direct
sunlight. IftheM27C1001isto beexposedto these
typesof lightingconditionsforextended periodsof
time,itis suggestedthat opaquelabels beput over
the M27C1001 window to prevent unintentional
erasure. The recommendederasure procedurefor
theM27C1001isexposuretoshortwaveultraviolet
light which has a wavelengthof 2537 Å. The inte-
grated dose (i.e. UV intensityx exposuretime) for
erasure should be a minimum of 15 W-sec/cm2.
Theerasuretime withthisdosageis approximately
15 to 20 minutes using an ultraviolet lamp with
12000 µW/cm2power rating. The M27C1001
should beplacedwithin 2.5 cm(1 inch) of the lamp
tubes during the erasure. Somelamps have afilter
on their tubes which should be removed before
erasure.
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M27C1001