M27W800 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M27W800 Datasheet PDF : 15 Pages
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Figure 8. Programming and Verify Modes AC Waveforms
A0-A18
Q0-Q15
BYTEVPP
VCC
E
G
tAVEL
DATA IN
tQVEL
VALID
tEHQX
DATA OUT
tVPHAV
tGLQV
tVCHAV
tELEH
tQXGL
PROGRAM
VERIFY
M27W800
tGHQZ
tGHAX
AI01599
Figure 9. Programming Flowchart
VCC = 6.25V, VPP = 12.5V
n=0
NO
++n
= 25
YES
E = 50µs Pulse
NO
VERIFY
YES
++ Addr
FAIL
Last NO
Addr
YES
CHECK ALL WORDS
BYTEVPP =VIH
1st: VCC = 5V
2nd: VCC = 2.7V
AI03600
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 overprogram pulse is applied since the
verify in MARGIN MODE at VCC much higher than
3.6V provides the necessary margin to each pro-
grammed cell.
Program Inhibit
Programming of multiple M27W800s in parallel
with different data is also easily accomplished. Ex-
cept for E, all like inputs including G of the parallel
M27W800 may be common. A TTL low level pulse
applied to a M27W800's E input and VPP at 12.5V,
will program that M27W800. A high level E input
inhibits the other M27W800s 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 VIH and G at VIL, VPP at 12.5V and VCC at
6.25V.
9/15
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