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M2732A-4F1 View Datasheet(PDF) - STMicroelectronics

Part Name
Description
Manufacturer
M2732A-4F1
ST-Microelectronics
STMicroelectronics ST-Microelectronics
M2732A-4F1 Datasheet PDF : 9 Pages
1 2 3 4 5 6 7 8 9
M2732A
Programming
When delivered, and after each erasure, all bits of
the M2732A are in the “1" state. Data is introduced
by selectively programming ”0’s" into the desired
bit locations. Although only “0’s” will be pro-
grammed, both “1’s” and “0’s” can be presented in
the data word. The only way to change a “0" to a
”1" is by ultraviolet light erasure.
The M2732A is in the programming mode when the
GVPP input is at 21V. A 0.1µF capacitor must be
placed across GVPP and ground to suppress spu-
rious voltage transients which may damage the
device. The data to be programmed is applied, 8
bits in parallel, to the data output pins. The levels
required for the address and data inputs are TTL.
When the address and data are stable, a 50ms,
active low, TTL program pulse is applied to the E
input. A program pulse must be applied at each
address location to be programmed. Any location
can be programmed at any time - either individually,
sequentially, or at random. The program pulse has
a maximum width of 55ms. The M2732A must not
be programmed with a DC signal applied to the E
input.
Programming of multiple M2732As in parallel with
the same data can be easily accomplished due to
the simplicity of the programming requirements.
Inputs of the paralleled M2732As may be con-
nected together when they are programmed with
the same data. A low level TTL pulse applied to the
E input programs the paralleled 2732As.
Program Inhibit
Programming of multiple M2732As in parallel with
different data is also easily accomplished. Except
for E, all like inputs (including GVPP) of the parallel
M2732As may be common. A TTL level program
pulse applied to a M2732A’s E input with GVPP at
21V will program that M2732A. A high level E input
inhibits the other M2732As from being pro-
grammed.
Program Verify
A verify should be performed on the programmed
bits to determine that they were correctly pro-
grammed. The verify is carried out with GVPP and
E at VIL.
ERASURE OPERATION
The erasure characteristics of the M2732A are
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 certain types of fluorescent lamps have wave-
lengths in the 3000-4000 Å range. Research shows
that constant exposure to room level fluorescent
lighting could erase a typical M2732A in approxi-
mately 3 years, while it would take approximately
1 week to cause erasure when exposed to the
direct sunlight. If the M2732A is to be exposed to
these types of lighting conditions for extended pe-
riods of time, it is suggested that opaque labels be
put over the M2732A window to prevent uninten-
tional erasure.
The recommended erasure procedure for the
M2732A is exposure to shortwave ultraviolet light
which has a wavelength of 2537 Å. The integrated
dose (i.e. UV intensity x exposure time) for erasure
should be a minimum of 15 W-sec/cm2. The era-
sure time with this dosage is approximately 15 to
20 minutes using an ultraviolet lamp with 12000
µW/cm2 power rating. The M2732A should be
placed within 2.5 cm of the lamp tubes during
erasure. Some lamps have a filter on their tubes
which should be removed before erasure.
Table 3. Operating Modes
Mode
Read
Program
Verify
Program Inhibit
Standby
Note: X = VIH or VIL.
E
VIL
VIL Pulse
VIL
VIH
VIH
GVPP
VIL
VPP
VIL
VPP
X
VCC
Q0 - Q7
VCC
Data Out
VCC
Data In
VCC
Data Out
VCC
Hi-Z
VCC
Hi-Z
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