AT91SAM7X256-AU(2006_02) データシートの表示（PDF） - Atmel Corporation

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AT91SAM7X256-AU
(Rev.:2006_02)

AT91 ARM® Thumb®-based Microcontrollers

Atmel Corporation 

9.4.3 Lock Regions

9.4.3.1

AT91SAM7X256

The Embedded Flash Controller manages 16 lock bits to protect 16 regions of the flash against

inadvertent flash erasing or programming commands. The AT91SAM7X256 contains 16 lock

regions and each lock region contains 64 pages of 256 bytes. Each lock region has a size of 16

Kbytes.

If a locked-region’s erase or program command occurs, the command is aborted and the EFC

trigs an interrupt.

The 16 NVM bits are software programmable through the EFC User Interface. The command

“Set Lock Bit” enables the protection. The command “Clear Lock Bit” unlocks the lock region.

Asserting the ERASE pin clears the lock bits, thus unlocking the entire Flash.

9.4.3.2

AT91SAM7X128

The Embedded Flash Controller manages 8 lock bits to protect 8 regions of the flash against

inadvertent flash erasing or programming commands. The AT91SAM7X128 contains 8 lock

regions and each lock region contains 64 pages of 256 bytes. Each lock region has a size of 16

Kbytes.

If a locked-region’s erase or program command occurs, the command is aborted and the EFC

trigs an interrupt.

The 8 NVM bits are software programmable through the EFC User Interface. The command “Set

Lock Bit” enables the protection. The command “Clear Lock Bit” unlocks the lock region.

Asserting the ERASE pin clears the lock bits, thus unlocking the entire Flash.

9.4.4

Security Bit Feature

The AT91SAM7X256/128 features a security bit, based on a specific NVM-Bit. When the secu-

rity is enabled, any access to the Flash, either through the ICE interface or through the Fast

Flash Programming Interface, is forbidden. This ensures the confidentiality of the code pro-

grammed in the Flash.

This security bit can only be enabled, through the Command “Set Security Bit” of the EFC User

Interface. Disabling the security bit can only be achieved by asserting the ERASE pin at 1, and

after a full flash erase is performed. When the security bit is deactivated, all accesses to the

flash are permitted.

It is important to note that the assertion of the ERASE pin should always be longer than 200 ms.

As the ERASE pin integrates a permanent pull-down, it can be left unconnected during normal

operation. However, it is safer to connect it directly to GND for the final application.

9.4.5

Non-volatile Brownout Detector Control

Two general purpose NVM (GPNVM) bits are used for controlling the brownout detector (BOD),

so that even after a power loss, the brownout detector operations remain in their state.

These two GPNVM bits can be cleared or set respectively through the commands “Clear Gen-

eral-purpose NVM Bit” and “Set General-purpose NVM Bit” of the EFC User Interface.

18 AT91SAM7X256/128 Preliminary

6120D–ATARM–02-Feb-06

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