ST7293 datasheet(22/69 Pages) STMICROELECTRONICS

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ST7294

EEPROM (Continued)

Note 1. Bytes must always be erased prior to

being written.

Note 2. E2LAT must be kept high during a time

period designated as tPROG and then be

cleared.

Note 3. When E2LAT is high, access to the

EEPROM array is impossible.

Note 4. It is impossible to perform successive

write or erase cycles without clearing

E2LAT.

Note 5. The device is delivered with the EEPROM

memory filled with the value FFh.

Warning:

User programs must not run from the

EEPROM (reserved for data only).

4.1.5 EEPROM Control Register

—

Read/Write

Reset Value: 0000 0000<N> (00h)

This register contains the bits required to read,

erase and program the EEPROM. They are de-

fined as follows:

Bits 7, 6, 5 = Reserved

Res

E2ERA

E2LAT

E2PGM

Bits 4,3 = Unused

Bit 2 = E2ERA

EEPROM Erase

E2ERA must be set to 1 for an erase operation. It

must be set after or at the same time as E2LAT. It

cannot be changed once 1 EEPROM address is

selected. It is held low when E2LAT is low. It is

therefore automatically reset when E2LAT is re-

set.

Bit 1 = E2LAT

EEPROM Latch Enable

When E2LAT is reset to 0, data can be read from

the EEPROM. When it is set to 1 and E2PGM re-

set to 0, a write into the EEPROM array causes

the data to be latched, according to the address

into one of 8 data registers. An additional bit is

latched to select the row. The selected columns

and row determine the locations involved in the

next erase or programming operation. E2LAT

must be cleared after each programming or erase

operation. E2ERA and E2PGM are forced low

when E2LAT is low.

Bit 0 = E2PGM

EEPROM Program Mode

This bit allows to switch on or off the internal

charge pump. When set to 1, the charge pump

generator is on: the high voltage is applied to the

EEPROM array. When low, the charge pump gen-

erator is off. E2PGM can only be reset by resetting

E2LAT.

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