ATSAMV7x

Reallocate RAM

The ATSAME70 device series gives the user the option to reallocate the RAM section, usually starting at 0x20400000, to other memory areas as TCM memory. Per default the RAM section is one block ranging from 256 - 384 KiB in size (depending on which specific device is used).

To reallocate the RAM the so called General Purpose NVM Bits can be used. More information can be found in the corresponding family user guide.

This setting needs to be taken into account when linking your application in the IDE as not all available RAM is necessarily in one memory region.

Read / Write Protection

Security Bit

Excerpt from the Microchip SAM E70/S70/V70/V71 data sheet:

The SAM [...]/V71 features a security bit based on the GPNVM bit 0. When security is enabled, any access to the Flash, SRAM, core registers and internal peripherals, either through the SW-DP, the ETM interface or the Fast Flash Programming Interface, is blocked. This ensures the confidentiality of the code programmed in the Flash. This security bit can only be enabled through the command “Set General-purpose NVM Bit 0” of the EEFC 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, SRAM, Core registers, Internal Peripherals are permitted.

Once the security bit is set, it will become effective immediately. The security bit can only be disabled from inside the application or via the ERASE-Pin. In order to set the security bit with J-Flash, the "Exit steps" can be used. An example J-Flash project that sets Bit 0 of GPNVM (= security bit) on a SAMV71Q21 target device can be found here: https://wiki.segger.com/File:ATSAMV71Q21_Secure.jflash

Sector Write Protection

At the start of a download to flash, J-Link automatically detects and removes any sector write protection before proceeding the flash programming.