m27c405 STMicroelectronics, m27c405 Datasheet - Page 8

• Manufacturer Part Number: m27c405
• Description: 4 Mbit 512kb X 8 Otp Eprom
• Manufacturer: STMicroelectronics

M27C405
Figure 6. Programming and Verify Modes AC Waveforms
PRESTO II Programming Algorithm
PRESTO II Programming Algorithm allows the
whole array to be programmed with a guaranteed
margin, in a typical time of 52.5 seconds. Pro-
gramming with PRESTO II consists of applying a
sequence of 100µs program pulses to each byte
until a correct verify occurs (see Figure 7). During
programming and verify operation, a MARGIN
MODE circuit is automatically activated in order to
guarantee that each cell is programmed with
enough margin. No overprogram pulse is applied
since the verify in MARGIN MODE provides the
necessary margin to each programmed cell.
Program Inhibit
Programming of multiple M27C405s in parallel
with different data is also easily accomplished. Ex-
cept for E, all like inputs including G of the parallel
M27C405 may be common. A TTL low level pulse
applied to a M27C405's E input, with V
12.75V, will program that M27C405. A high level E
input inhibits the other M27C405s from being pro-
grammed.
8/14
V CC
A0-A18
Q0-Q7
V PP
E
G
tVPHEL
tVCHEL
tQVEL
tAVPL
tELEH
DATA IN
PROGRAM
PP
at
VALID
tEHQX
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
On-Board Programming
Programming the M27C405 may be performed di-
rectly in the application circuit, however this re-
quires modification to the PRESTO II Algorithm
(see Figure 8). For in-circuit programming V
determined by the user and normally is compatible
with other components using the same supply volt-
age. It is recommended that the maximum value of
V
used.
Typically V
ing V
does not affect the programming, it gives a higher
test capability in VERIFY mode.
V
enable the programming.
CC
PP
tQXGL
IL
must be kept at 12.75 volts to maintain and
which remains compatible with the circuit is
CC
, E at V
VERIFY
tGLQV
= 5V is recommended. The value of V
DATA OUT
CC
IH
= 5.5V for programming systems us-
, V
PP
at 12.75V and V
tGHQZ
tGHAX
AI00725
CC
at 6.25V.
CC
CC
is