M27W801 datasheet(9/16 Pages) STMICROELECTRONICS

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M27W801

PRESTO IIB Programming Algorithm

PRESTO IIB Programming Algorithm allows the

whole array to be programmed with a guaranteed

margin, in a typical time of 52.5 seconds. This can

be achieved with STMicroelectronics M27W801

due to several design innovations to improve pro-

gramming efficiency and to provide adequate mar-

gin for reliability. Before starting the programming

the internal MARGIN MODE circuit must be set in

order to guarantee that each cell is programmed

with enough margin. Then a sequence of 50

µs

program pulses are applied to each byte until a

correct verify occurs (see Figure 8). No overpro-

gram pulses are applied since the verify in MAR-

GIN MODE at VCC much higher than 3.6V,

provides the necessary margin.

Program Inhibit

Programming of multiple M27W801s in parallel

with different data is also easily accomplished. Ex-

cept for E, all like inputs including GVPP of the par-

allel M27W801 may be common. A TTL low level

pulse applied to a M27W801’s E input, with VPP at

12.75V, will program that M27W801. A high level

E input inhibits the other M27W801s 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 VIL. Data should be verified with tELQV after the

falling edge of E.

Figure 7. Programming and Verify Modes AC Waveforms

tAVEL

VALID

AI01270

A0-A19

Q0-Q7

VCC

DATA IN

DATA OUT

tQVEL

tVCHEL

tVPHEL

tEHQX

tEHVPX

tELQV

tELEH

tEHQZ

tVPLEL

PROGRAM

VERIFY

GVPP

tEHAX

Figure 8. Programming Flowchart

AI01271C

n= 0

Last

Addr

VERIFY

E= 50

µs Pulse

++n

=25

++ Addr

VCC = 6.25V, VPP = 12.75V

FAIL

CHECK ALL BYTES

1st: VCC =5V

2nd: VCC = 2.7V

YES

SET MARGIN MODE

RESET MARGIN MODE

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