AT91SAM7S64 datasheet(20/42 Pages) ATMEL

20 / 42 page

6175BS–ATARM–04-Nov-05

AT91SAM7S Series Summary

If a locked-regions 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.

9.6.4

Security Bit Feature

The AT91SAM7S Series features a security bit, based on a specific NVM-Bit. When the security

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 programmed 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

50 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.

9.6.5

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.

• GPNVM Bit 0 is used as a brownout detector enable bit. Setting the GPNVM Bit 0 enables

the BOD, clearing it disables the BOD. Asserting ERASE clears the GPNVM Bit 0 and thus

disables the brownout detector by default.

• The GPNVM Bit 1 is used as a brownout reset enable signal for the reset controller. Setting

the GPNVM Bit 1 enables the brownout reset when a brownout is detected, Clearing the

GPNVM Bit 1 disables the brownout reset. Asserting ERASE disables the brownout reset by

default.

9.6.6

Calibration Bits

Eight NVM bits are used to calibrate the brownout detector and the voltage regulator. These bits

are factory configured and cannot be changed by the user. The ERASE pin has no effect on the

calibration bits.

9.7

Fast Flash Programming Interface

The Fast Flash Programming Interface allows programming the device through either a serial

JTAG interface or through a multiplexed fully-handshaked parallel port. It allows gang-program-

ming with market-standard industrial programmers.

The FFPI supports read, page program, page erase, full erase, lock, unlock and protect

commands.

The Fast Flash Programming Interface is enabled and the Fast Programming Mode is entered

when the TST pin and the PA0 and PA1 pins are all tied high and PA2 is tied low.

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