BL7448SM データシートの表示（PDF） - Shanghai Belling Co., Ltd.

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BL7448SM

Intelligent 8K-bit EEPROM

Shanghai Belling Co., Ltd. 

Function Description

Block Diagram

BL7448SM Intelligent 8K-bit

EEPROM

Figure 2

The BL7448SM consists of 1024 x 8 bit EEPROM main memory and a 1024-bit protection-memory

With PROM functionality .The main memory can be irreversibly protected against data change by writing the

corresponding bit in the protection memory. Once written the protection bit cannot be erased. The main

memory is erased and written byte by byte. Normally a data change consists of an erase and write

procedure. It depends on the contents of the data byte in the main memory and the new data byte whether

the EEPROM is really erased and/or written. If none of the 8 bits in the addressed byte requires a zero-to-

one transition the erase access will be suppressed. Vice versa the write access will be suppressed if no one-

to-zero transition is necessary.

Additionally to the above functions the BL7448SM provides a security code logic, which

controls the write/erase access to the memory. For this purpose, the BL7448SM contains a 3-

byte security memory with an error counter EC and 2 bytes reference data. These 2 bytes as a

whole are called programmable security code (PSC). After power on the whole memory, except

for the reference data, the memory can only be read. (The value of PSC is “00”)Writing and

erasing is only possible after a successful comparison of verification data with the internal

reference data.

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Total 7 Pages

8/16/2006

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