M27C4002 Device operation
11/24
M27C4002, these two identifier bytes are given in Table 3: Electronic Signature and can be
read-out on outputs Q7 to Q0.
2.10 Erasure operation (applies to UV EPROM)
The erasure characteristics of the M27C4002 are 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 M27C4002 in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M27C4002 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 M27C4002 window to prevent unintentional erasure. The recommended
erasure procedure for the M27C4002 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 W-sec/cm
2
. The erasure time with this dosage is approximately
15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm
2
power rating. The M27C4002
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 removed before erasure.
Table 2. Operating modes
(1)
1. X = V
IH
or V
IL
, V
ID
= 12V ± 0.5V.
Mode E G A9 V
PP
Q15-Q0
Read V
IL
V
IL
XV
CC
or V
SS
Data Out
Output Disable V
IL
V
IH
XV
CC
or V
SS
Hi-Z
Program V
IL
Pulse V
IH
XV
PP
Data In
Verify V
IH
V
IL
XV
PP
Data Out
Program Inhibit V
IH
V
IH
XV
PP
Hi-Z
Standby V
IH
XXV
CC
or V
SS
Hi-Z
Electronic Signature V
IL
V
IL
V
ID
V
CC
Codes
Table 3. Electronic Signature
(1)
1. Outputs Q15-Q8 are set to '0'.
Identifier A0 Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 Hex Data
Manufacturer’s
Code
V
IL
00100000 20h
Device Code V
IH
01000100 44h
Obsolete Product(s) - Obsolete Product(s)
