OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

M27C256B-70C6

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
7/16
M27C256B
Table 9. Programming Mode DC Characteristics
(1)
(T
A
= 25 °C; V
CC
= 6.25V ± 0.25V; V
PP
= 12.75V ± 0.25V)
Note: V
CC
must be applied simultaneously with or before V
PP
and removed simultaneously or after V
PP
.
Table 10. Programming Mode AC Characteristics
(1)
(T
A
= 25 °C; V
CC
= 6.25V ± 0.25V; V
PP
= 12.75V ± 0.25V
Note: V
CC
must be applied simultaneously with or before V
PP
and removed simultaneously or after V
PP
.
Symbol Parameter Test Condition Min Max Unit
I
LI
Input Leakage Current
V
IL
≤
V
IN
≤
V
IH
±10 µA
I
CC
Supply Current 50 mA
I
PP
Program Current
E
= V
IL
50 mA
V
IL
Input Low Voltage –0.3 0.8 V
V
IH
Input High Voltage 2
V
CC
+ 0.5
V
V
OL
Output Low Voltage
I
OL
= 2.1mA
0.4 V
V
OH
Output High Voltage TTL
I
OH
= –1mA
3.6 V
V
ID
A9 Voltage 11.5 12.5 V
Symbol Alt Parameter Test Condition Min Max Unit
t
AVEL
t
AS
Address Valid to Chip Enable Low 2 µs
t
QVEL
t
DS
Input Valid to Chip Enable Low 2 µs
t
VPHEL
t
VPS
V
PP
High to Chip Enable Low
2µs
t
VCHEL
t
VCS
V
CC
High to Chip Enable Low
2µs
t
ELEH
t
PW
Chip Enable Program Pulse Width 95 105 µs
t
EHQX
t
DH
Chip Enable High to Input Transition 2 µs
t
QXGL
t
OES
Input Transition to Output Enable Low 2 µs
t
GLQV
t
OE
Output Enable Low to Output Valid 100 ns
t
GHQZ
t
DFP
Output Enable High to Output Hi-Z 0 130 ns
t
GHAX
t
AH
Output Enable High to Address Transition 0 ns
Programming
When delivered (and after each erasure for UV
EPROM), all bits of the M27C256B are in the "1"
state. Data is introduced by selectively program-
ming "0"s into the desired bit locations. Although
only "0"s will be programmed, both "1"s and "0"s
can be present in the data word. The only way to
change a '0' to a '1' is by die exposure to ultraviolet
light (UV EPROM). The M27C256B is in the pro-
gramming mode when V
PP
input is at 12.75V, G is
at V
IH
and E is pulsed to V
IL
. The data to be pro-
grammed is applied to 8 bits in parallel to the data
output pins. The levels required for the address
and data inputs are TTL. V
CC
is specified to be
6.25V ± 0.25 V.
M27C256B
8/16
PRESTO II Programming Algorithm
PRESTO II Programming Algorithm allows to pro-
gram the whole array with a guaranteed margin, in
a typical time of 3.5 seconds. Programming with
PRESTO II involves the application of a sequence
of 100µs program pulses to each byte until a cor-
rect verify occurs (see Figure 7). During program-
ming and verify operation, a MARGIN MODE
circuit is automatically activated in order to guar-
antee that each cell is programmed with enough
margin. No overprogram pulse is applied since the
verify in MARGIN MODE provides necessary mar-
gin to each programmed cell.
Program Inhibit
Programming of multiple M27C256Bs in parallel
with different data is also easily accomplished. Ex-
cept for E
, all like inputs including G of the parallel
M27C256B may be common. A TTL low level
pulse applied to a M27C256B's E
input, with V
PP
at 12.75V, will program that M27C256B. A high
level E
input inhibits the other M27C256Bs from
being programmed.
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 G
at V
IL
, E at V
IH
, V
PP
at 12.75V and V
CC
at 6.25V.
Figure 6. Programming and Verify Modes AC Waveforms
tAVEL
VALID
AI00759
A0-A14
Q0-Q7
V
PP
V
CC
G
DATA IN DATA OUT
E
tQVEL
tVPHEL
tVCHEL
tEHQX
tELEH
tGLQV
tQXGL
tGHQZ
tGHAX
PROGRAM VERIFY
Figure 7. Programming Flowchart
AI00760B
n = 0
Last
Addr
VERIFY
E = 100µs Pulse
++n
= 25
++ Addr
V
CC
= 6.25V, V
PP
= 12.75V
FAIL
CHECK ALL BYTES
1st: V
CC
= 6V
2nd: V
CC
= 4.2V
YES
NO
YES
NO
YES
NO
9/16
M27C256B
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 M27C256B. To activate the ES
mode, the programming equipment must force
11.5V to 12.5V on address line A9 of the
M27C256B, with V
CC
= V
PP
= 5V. Two identifier
bytes may then be sequenced from the device out-
puts by toggling address line A0 from V
IL
to V
IH
. All
other address lines must be held at V
IL
during
Electronic Signature mode. Byte 0 (A0 = V
IL
) rep-
resents the manufacturer code and byte 1
(A0 = V
IH
) the device identifier code. For the ST-
Microelectronics M27C256B, these two identifier
bytes are given in Table 4 and can be read-out on
outputs Q7 to Q0.
ERASURE OPERATION (applies for UV EPROM)
The erasure characteristics of the M27C256B 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 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 pe-
riods of time, it is suggested that opaque labels be
put over the M27C256B window to prevent unin-
tentional erasure. The recommended erasure pro-
cedure for the M27C256B is exposure to short
wave ultraviolet light which has wavelength
2537Å. The integrated dose (i.e. UV intensity x ex-
posure 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 ultravi-
olet lamp with 12000 µW/cm
2
power rating. The
M27C256B 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.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

M27C256B-70C6

Mfr. #:
Buy M27C256B-70C6
Manufacturer:
STMicroelectronics
Description:
EPROM 256K (32KX8) 70ns
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet