Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

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SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]

11063K–ATARM–05-Nov-13

In order to bring security to the TWI, a write protection system has been implemented.

The write protection mode prevents the write of the 

 and the 

. When this mode is enabled and one of the protected registers is written, an error is generated in the 

 and the register write request is canceled. When a write protection error occurs the

WPVS flag is set and the address of the corresponding canceled register write is available in the WPVSRC field of the

Due to the nature of the write protection feature, enabling and disabling the write protection mode requires the use of a
security code. Thus when enabling or disabling the write protection mode the WPKEY field of the 

 must be filled with the “TWI” ASCII code (0x545749) otherwise the register write will be canceled.