M27C400-100B6TR STMICROELECTRONICS [STMicroelectronics], M27C400-100B6TR Datasheet - Page 10

• Manufacturer Part Number: M27C400-100B6TR
• Description: 4 Mbit 512Kb x8 or 256Kb x16 UV EPROM and OTP EPROM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M27C400
Figure 9. Programming Flowchart
PRESTO III Programming Algorithm
The PRESTO III Programming Algorithm allows
the whole array to be programed with a guaran-
teed margin in a typical time of 26 seconds. Pro-
gramming with PRESTO III consists of applying a
sequence of 50µs program pulses to each word
until a correct verify occurs (see Figure 9). During
programing and verify operation a MARGIN
MODE circuit is automatically activated to guaran-
tee that each cell is programed with enough mar-
gin. No overpromise pulse is applied since the
verify in MARGIN MODE provides the necessary
margin to each programmed cell.
Program Inhibit
Programming of multiple M27C400s in parallel
with different data is also easily accomplished. Ex-
cept for E, all like inputs including G of the parallel
M27C400 may be common. A TTL low level pulse
applied to a M27C400's E input and V
will program that M27C400. A high level E input in-
hibits the other M27C400s from being pro-
grammed.
Program Verify
A verify (read) should be performed on the pro-
grammed bits to determine that they were correct-
ly programmed. The verify is accomplished with E
at V
6.25V.
10/14
IH
YES
NO
and G at V
FAIL
= 25
++n
V CC = 6.25V, V PP = 12.5V
CHECK ALL WORDS
NO
2nd: V CC = 4.2V
BYTEV PP =V IH
1st: V CC = 6V
E = 50 s Pulse
IL
, V
VERIFY
n = 0
Addr
Last
PP
YES
YES
at 12.5V and V
NO
++ Addr
AI01044B
PP
at 12.5V,
CC
at
On-Board Programming
The M27C400 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 ± 5°C am-
bient temperature range that is required when pro-
gramming the M27C400. To activate the ES
mode, the programming equipment must force
11.5V to 12.5V on address line A9 of the
M27C400, with V
bytes may then be sequenced from the device out-
puts by toggling address line A0 from V
other address lines must be held at V
Electronic Signature mode.
Byte 0 (A0 = V
code and byte 1 (A0 = V
code. For the STMicroelectronics M27C400, these
two identifier bytes are given in Table 4 and can be
read-out on outputs Q7 to Q0.
ERASURE OPERATION (applies to UV EPROM)
The erasure characteristics of the M27C400 is
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 some type of fluorescent lamps have
wavelengths in the 3000-4000 Å range. Research
shows that constant exposure to room level fluo-
rescent lighting could erase a typical M27C400 in
about 3 years, while it would take approximately 1
week to cause erasure when exposed to direct
sunlight. If the M27C400 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 M27C400 window to prevent unintentional era-
sure. The recommended erasure procedure for
M27C400 is exposure to short wave ultraviolet
light which has a wavelength of 2537 Å. The inte-
grated dose (i.e. UV intensity x exposure time) for
erasure should be a minimum of 30 W-sec/cm
The erasure time with this dosage is approximate-
ly 30 to 40 minutes using an ultraviolet lamp with
12000 µW/cm
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.
2
IL
) represents the manufacturer
power rating. The M27C400
PP
= V
CC
IH
) the device identifier
= 5V. Two identifier
IL
to V
IL
during
IH
. All
2
.