M27C256B-20C1 STMicroelectronics, M27C256B-20C1 Datasheet - Page 11

• Manufacturer Part Number: M27C256B-20C1
• Manufacturer: STMicroelectronics

Specifications of M27C256B-20C1

• Lead Free Status / RoHS Status: Supplier Unconfirmed

M27C256B
2.10
Erasure operation (applies for UV EPROM)
The erasure characteristics of the M27C256B 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 M27C256B in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M27C256B 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 M27C256B window to prevent unintentional erasure. The recommended
erasure procedure for the M27C256B is exposure to short wave ultraviolet light which has
wavelength 2537Å. The integrated dose (i.e. UV intensity x exposure time) for erasure
should be a minimum of 15 W-sec/cm
15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm
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.
Table 2.
1. X = V
Table 3.
Read
Output Disable
Program
Verify
Program Inhibit
Standby
Electronic Signature
Manufacturer’s
Code
Device Code
Identifier
IH
or V
Mode
IL
Operating modes
Electronic signature
, V
ID
= 12V ± 0.5V.
V
A0
V
IH
IL
V
Q7
0
1
IL
V
V
V
V
V
V
Pulse
E
(1)
IH
IH
IH
IL
IL
IL
Q6
0
0
2
. The erasure time with this dosage is approximately
Q5
1
0
V
V
V
V
V
V
G
X
IH
IH
IH
IL
IL
IL
Q4
0
0
Q3
0
1
V
A9
X
X
X
X
X
X
ID
2
power rating. The M27C256B
Q2
0
1
V
V
V
V
Q1
V
V
V
V
0
0
PP
CC
CC
PP
PP
PP
CC
CC
Device operation
Q0
0
1
Data Out
Data Out
Data In
Q7-Q0
Codes
Hex Data
Hi-Z
Hi-Z
Hi-Z
8Dh
20h
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