M27V401 datasheet(8/15 Pages) STMICROELECTRONICS

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M27V401

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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 involves in applying a

sequence of 100

µs 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 at VCC much

higher than 3.6V provides necessary margin to

each programmed cell.

Program Inhibit

Programming of multiple M27V401s in parallel

with different data is also easily accomplished. Ex-

cept for E, all like inputs including G of the parallel

M27V401 may be common. A TTL low level pulse

applied to a M27V401’s E input with VPP at

12.75V, will program that M27V401. A high level E

input inhibits the other M27V401s 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.

Figure 6. Programming and Verify Modes AC Waveforms

tAVPL

VALID

AI00725

A0-A18

Q0-Q7

VPP

VCC

DATA IN

DATA OUT

tQVEL

tVPHEL

tVCHEL

tEHQX

tELEH

tGLQV

tQXGL

tGHQZ

tGHAX

PROGRAM

VERIFY

Figure 7. Programming Flowchart

AI00760B

n= 0

Last

Addr

VERIFY

E = 100

µs Pulse

++n

=25

++ Addr

VCC = 6.25V, VPP = 12.75V

FAIL

CHECK ALL BYTES

1st: VCC =6V

2nd: VCC = 4.2V

YES

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