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AS3953

Datasheet - D e t a il e d D es c r i pt io n

7.9.4 OTP Words

Write and Read Lock Words are OTP (One Time Programmable). This means that once they are set to ‘1’, they cannot be reset back to ‘0’. Since

setting of OTP bits is an irreversible operation, it is strongly recommended to perform it in controlled environment.

7.9.5 Write Lock Word

The Write Lock Word contains write lock bits. Each EEPROM word has a corresponding lock bit in the Write Lock Word. Once a certain lock bit

is set to ‘1’, the content of corresponding word cannot be modified any more (it becomes read only), EEPROM write commands issued either

through PICC interface or through SPI interface are rejected. The lock bit of a certain number protects the word with the same number (e.g.

b5 of

lock word protects word 5). Since lock bits are OTP they cannot be reset back to ‘0’ once they are set to ‘1’.Therefore once a certain word is

locked it cannot be unlocked any more. The lock bits for page 0 is “don’t care” since word 0 is always read only. Please note that setting lock bit

b2 locks the Lock Word itself, therefore once this bit is set the lock configuration cannot be modified any more.

7.9.6 Read Lock Word

The Read Lock Word contains read lock bits. Each EEPROM word has a corresponding lock bit in the Read Lock Word. Once a certain lock bit

is set to ‘1’, the content of corresponding word cannot be read through PICC interface, it can only be read through SPI interface. The lock bit of a

certain number protects the word with the same number (e.g.

b5 of lock word protects word 5). Since lock bits are OTP they cannot be reset back

to ‘0’ once they are set to ‘1’. Therefore once a certain word is locked it cannot be unlocked any more. The lock bits for pages 0 to 4 are “don’t

care”; these pages can be read through PICC interface even in case their corresponding lock bits are set.