ST92F120 datasheet(49/324 Pages) STMICROELECTRONICS

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ST92F120 - SINGLE VOLTAGE FLASH & EEPROM

EEPROM (Cont’d)

3.5.2 EEPROM Update Operation

The update of the EEPROM content can be made

by pages of 16 consecutive bytes. The Page Up-

date operation allows up to 16 bytes to be loaded

into the RAM buffer that replace the ones already

contained in the specified address.

Each time a Page Update operation is executed in

the EEPROM, the RAM buffer content is pro-

grammed in the next free block relative to the

specified page (the RAM buffer is previously auto-

matically filled with old data for all the page ad-

dresses not selected for updating). If all the 4

blocks of the specified page in the current EEP-

ROM sector are full, the page content is copied to

the complementary sector, that becomes the new

current one.

After that the specified page has been copied to

the next free block, one erase phase is executed

on the complementary sector, if the 4 erase phas-

es have not yet been executed. When the selected

page is copied to the complementary sector, the

remaining 63 pages are also copied to the first

block of the new sector; then the first erase phase

is executed on the previous full sector. All this is

executed in a hidden manner, and the End Page

Update Interrupt is generated only after the end of

the complete operation.

At Reset the two status pages are read in order to

detect which is the sector that is currently mapping

the EEPROM, and in which block each page is

mapped. A system defined routine written in Test-

Flash is executed at reset, so that any previously

aborted write operation is restarted and complet-

ed.

Figure 24. Hardware Emulation Flow

Emulation Flow

Reset

Read Status Pages

Map EEPROM

in current sector

Write operation

to complete ?

Complete

Write operation

Update

Status page

Yes

Wait for

Update commands

Page

Update

Command

End Page

Update

Interrupt

(to Core)

Program selected

Page from RAM buffer

in next free block

Copy all other Pages

into RAM buffer;

then program them

in next free block

1/4 erase of

complementary sector

Update

Status Page

new

sector ?

Yes

Complementary

sector erased ?

Yes

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