M27C512 STMicroelectronics, M27C512 Datasheet - Page 9

• Manufacturer Part Number: M27C512
• Description: 512 Kbit 64Kb x8 UV EPROM and OTP EPROM
• Manufacturer: STMicroelectronics

Figure 8. Programming Flowchart
PRESTO IIB Programming Algorithm
PRESTO IIB Programming Algorithm allows the
whole array to be programmed with a guaranteed
margin, in a typical time of 6.5 seconds. This can
be achieved with STMicroelectronics M27C512
due to several design innovations described in the
M27C512 datasheet to improve programming effi-
ciency and to provide adequate margin for reliabil-
ity. Before starting the programming the internal
MARGIN MODE circuit is set in order to guarantee
that each cell is programmed with enough margin.
Then a sequence of 100 s program pulses are
applied to each byte until a correct verify occurs.
No overprogram pulses are applied since the verify
in MARGIN MODE provides the necessary margin.
Program Inhibit
Programming of multiple M27C512s in parallel with
different data is also easily accomplished. Except
for E, all like inputs including GV
M27C512 may be common. A TTL low level pulse
applied to a M27C512’s E input, with V
will program that M27C512. A high level E input
inhibits the other M27C512s from being pro-
grammed.
Program Verify
A verify (read) should be performed on the pro-
grammed bits to determine that they were correctly
YES
NO
FAIL
= 25
++n
V CC = 6.25V, V PP = 12.75V
RESET MARGIN MODE
SET MARGIN MODE
CHECK ALL BYTES
NO
2nd: V CC = 4.2V
E = 100 s Pulse
1st: V CC = 6V
VERIFY
n = 0
Addr
Last
YES
YES
NO
PP
++ Addr
of the parallel
PP
AI00738B
at 12.75V,
programmed. The verify is accomplished with G at
V
falling edge of E.
On-Board Programming
The M27C512 can be directly programmed in the
application circuit. See the relevant Application
Note AN620.
Electronic Signature
The Electronic Signature (ES) 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. The
ES mode is functional in the 25 C
temperature range that is required when program-
ming the M27C512. To activate the ES mode, the
programming equipment must force 11.5V to 12.5V
on address line A9 of the M27C512. Two identifier
bytes may then be sequenced from the device
outputs by toggling address line A0 from V
All other address lines must be held at V
Electronic Signature mode.
Byte 0 (A0=V
and byte 1 (A0=V
the STMicroelectronics M27C512, these two iden-
tifier bytes are given in Table 4 and can be read-out
on outputs Q0 to Q7.
ERASURE OPERATION (appl ies for UV
EPROM)
The erasure characteristics of the M27C512 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
M27C512 in about 3 years, while it would take
approximately 1 week to cause erasure when ex-
posed to direct sunlight. If the M27C512 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 M27C512 window to
prevent unintentional erasure. The recommended
erasure procedure for the M27C512 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
is approximately 15 to 20 minutes using an ultra-
violet lamp with 12000 W/cm
M27C512 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 re-
moved before erasure.
IL
. Data should be verified with t
IL
) represents the manufacturer code
2
. The erasure time with this dosage
IH
) the device identifier code. For
2
power rating. The
ELQV
5 C ambient
M27C512
after the
IL
IL
during
to V
9/15
IH
.