AI00774B

n = 1

Last

Addr

VERIFY

E = 1ms Pulse

++n

> 25

++ Addr

VCC = 6V, VPP = 12.5V

FAIL

CHECK ALL BYTES

VCC = 5V, VPP = 5V

YES

NO

YES

NO

YES

NO

E = 3ms Pulse by n

Figure 8. Fast Programming Flowchart

AI00773B

n = 0

Last

Addr

VERIFY

E = 500

µs Pulse

++n

= 25

++ Addr

VCC = 6.25V, VPP = 12.75V

FAIL

CHECK ALL BYTES

VCC = 5V, VPP = 5V

YES

NO

YES

NO

YES

NO

SET MARGIN MODE

RESET MARGIN MODE

Figure 9. PRESTO Programming Flowchart

DEVICE OPERATION (cont’d)

The Fast Programming Algorithm utilizes two differ-

ent pulse types : initial and overprogram. The du-

ration of the initial E pulse(s) is 1ms, which will then

be followed by a longer overprogram pulse of length

3ms by n (n is an iteration counter and is equal to

the number of the initial one millisecond pulses

applied to a particular M27512 location), before a

correct verify occurs. Up to 25 one-millisecond

pulses per byte are provided for before the over

program pulse is applied.

The entire sequence of program pulses is per-

Programming cycle has been completed, all bytes

should be compared to the original data with

PRESTO Programming Algorithm

PRESTO Programming Algorithm allows to pro-

gram the whole array with a guaranted margin, in

a typical time of less than 50 seconds (to be com-

pared with 283 seconds for the Fast algorithm).

This can be achieved with the STMicroelectronics

M27512 due to several design innovations de-

scribed in the next paragraph that improves pro-

gramming efficiency and brings adequate margin

for reliability. Before starting the programming the

internal MARGIN MODE circuit is set in order to

guarantee that each cell is programmed with

enough margin.

Then a sequence of 500

µs program pulses are

applied to each byte until a correct verify occurs.

No overprogram pulses are applied since the verify

in MARGIN MODE provides the necessary margin

to each programmed cell.

Program Inhibit

Programming of multiple M27512s in parallel with

different data is also easily accomplished. Except

M27512 may be common. A TTL low level pulse

will program that M27512. A high level E input

inhibits the other M27512s from being pro-

grammed.

Program Verify

A verify (read) should be performed on the pro-

grammed bits to determine that they were correctly

falling edge of E.

M27512

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