M28F201 datasheet(16/21 Pages) STMICROELECTRONICS

16 / 21 page

PRESTO F ERASE ALGORITHM

The PRESTO F Erase Algorithm guarantees that

the device will be erased in a reliable way. The

algorithm first programs all bytes to 00h in order to

ensure uniform erasure. The programming follows

the PRESTO F Programming Algorithm. Erase is

set-up by writing 20h to the command register, the

erasure is started by repeating this write cycle.

Erase Verify is set-up by writing A0h to the com-

mand register together with the address of the byte

to be verified. The subsequent read cycle reads the

data which is compared to FFh. Erase Verify begins

at address 0000h and continues to the last address

or until the comparison of the data to FFh fails. If

this occurs, the address of the last byte checked is

stored and a new Erase operation performed.

Erase Verify then continues from the address of the

stored location.

PRESTO F PROGRAM ALGORITHM

The PRESTO F Programming Algorithm applies a

series of 10

µs programming pulses to a byte until

a correct verify occurs. Up to 25 programming

operations are allowed for one byte. Program is

set-up by writing 40h to the command register, the

programming is started after the next write cycle

which also latches the address and data to be

programmed. Program Verify is set-up by writing

C0h to the command register, followed by a read

cycle and a compare of the data read to the data

expected. During Program and Program Verify op-

erations a MARGIN MODE circuit is activated to

guarantee that the cell is programmed with a safety

margin.

PROGRAM ALL

BYTES TO 00h

AI00649

n=0, Addr=00000h

Last

Addr

ERASE SET-UP

Wait 10ms

ERASE VERIFY

Latch Addr.

READ DATA OUTPUT

Data

Wait 6

µs

++n

Addr++

READ COMMAND

VPP = 12V

VPP < 6.5V

FAIL

VPP < 6.5V, PASS

YES

1000

Figure 12. Erasing Flowchart

AI00677

n= 0

Last

Addr

PROGRAM VERIFY

Wait 10

µs

PROGRAM SET-UP

Latch Addr, Data

READ DATA OUTPUT

Data

Wait 6

µs

++n

=25

Addr++

READ COMMAND

VPP = 12V

VPP < 6.5V

FAIL

VPP < 6.5V, PASS

YES

Figure 13. Programming Flowchart

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