M27V405 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
View to exact match
M27V405 Datasheet PDF : 13 Pages
| |||
M27V405
Figure 6. Programming and Verify Modes AC Waveforms
A0-A18
Q0-Q7
VPP
VCC
E
G
tAVPL
DATA IN
tQVEL
tVPHEL
tVCHEL
tELEH
VALID
tEHQX
DATA OUT
tGLQV
tQXGL
tGHQZ
tGHAX
PROGRAM
VERIFY
AI00725
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 100ms 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 M27V405s in parallel
with different data is also easily accomplished. Ex-
cept for E, all like inputs including G of the parallel
M27V405 may be common. A TTL low level pulse
applied to a M27V405’s E input, with VPP at
12.75V, will program that M27V405. A high level E
input inhibits the other M27V405s 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 G
at VIL , E at VIH, VPP at 12.75V and VCC at 6.25V.
On-Board Programming
Programming the M27V405 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 VCC is
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
VCC which remains compatible with the circuit is
used.
Typically VCC=5.5V for programming systems us-
ing VCC=5V, and VCC=3.5V for low voltage 3V
systems is recommended. The value of VCC does
not affect the programming, it gives a higher test
capability in VERIFY mode.
VPP must be kept at 12.75 volts to maintain and
enable the programming.
8/13
Share Link: 