27C160 datasheet(10/19 Pages) STMICROELECTRONICS

10 / 19 page

M27C160

10/19

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 52.5 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 11). 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 provides the necessary

margin to each programmed cell.

Program Inhibit

Programming of multiple M27C160s in parallel

with different data is also easily accomplished. Ex-

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

M27C160 may be common. A TTL low level pulse

applied to a M27C160's E input and VPP at 12.5V,

will program that M27C160. A high level E input in-

hibits the other M27C160s 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.

Figure 10. Programming and Verify Modes AC Waveforms

tAVEL

VALID

AI00744

A0-A19

Q0-Q15

BYTEVPP

VCC

DATA IN

DATA OUT

tQVEL

tVPHAV

tVCHAV

tEHQX

tELEH

tGLQV

tQXGL

tGHQZ

tGHAX

PROGRAM

VERIFY

Figure 11. Programming Flowchart

AI01044B

n = 0

Last

Addr

VERIFY

E = 50

µs Pulse

++n

= 25

++ Addr

VCC = 6.25V, VPP = 12.5V

FAIL

CHECK ALL WORDS

BYTEVPP =VIH

1st: VCC = 6V

2nd: VCC = 4.2V

YES

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