Datasheet

Note: 1) Default value is 0x7.
The EEPROM[2:0] bits indicate the EEPROM size, see the table below. The EEPROM resides in the
upper rows of the NVM main address space and is writable, regardless of the region lock status.
Table 22-3. EEPROM Size
EEPROM[2:0] Rows Allocated to EEPROM EEPROM Size in Bytes
7 None 0
6 1 256
5 2 512
4 4 1024
3 8 2048
2 16 4096
1 32 8192
0 64 16384
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10.2 Physical Memory Map
22.6.6 Security Bit
The security bit allows the entire chip to be locked from external access for code security. The security bit
can be written by a dedicated command, Set Security Bit (SSB). Once set, the only way to clear the
security bit is through a debugger Chip Erase command. After issuing the SSB command, the PROGE
error bit can be checked.
In order to increase the security level it is recommended to enable the internal BOD33 when the security
bit is set.
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13. DSU - Device Service Unit
22.6.7 Cache
The NVM Controller cache reduces the device power consumption and improves system performance
when wait states are required. Only the NVM main array address space is cached. It is a direct-mapped
cache that implements 8 lines of 64 bits (i.e., 64 Bytes). NVM Controller cache can be enabled by writing
a '0' to the Cache Disable bit in the Control B register (CTRLB.CACHEDIS).
The cache can be configured to three different modes using the Read Mode bit group in the Control B
register (CTRLB.READMODE).
The INVALL command can be issued using the Command bits in the Control A register to invalidate all
cache lines (CTRLA.CMD=INVALL). Commands affecting NVM content automatically invalidate cache
lines.
SAM D21 Family
NVMCTRL – Nonvolatile Memory Controller
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 391