29.5.9 Silent Access

When enabled (SECCTRL.SILACC = 1), the silent access feature allows to store data and their 1's complement in one Data Flash row (selected by SECCTRL.TEROW), thus reducing the overall data reading noise, as always the same number of '0' and '1' will be read for each read access.

When Silent Access is enabled, the logical size of the TEROW Flash row is divided by two to store each byte of Data and its 1’s complement (CompData) in the whole physical TEROW size.

The data stored in the selected TEROW must be accessed using the logical mapping shown in the TEROW logical mapping table.

Table 29-2. TEROW logical mapping (SECCTRL.SILACC=1)
Byte 63Byte 62Byte 61…Byte 3Byte 2Byte 1Byte 0Page
Data Data Data Data Data Data Data Data0
Data Data Data Data Data Data Data Data1
ReservedReservedReservedReservedReservedReservedReservedReserved2
ReservedReservedReservedReservedReservedReservedReservedReserved3
Note: All accesses to the reserved area of the TEROW are discarded and generate a bus error.

The physical mapping of the TEROW, when silent access feature is enabled, is represented in the TEROW physical mapping table:

Table 29-3. TEROW physical mapping (SECCTRL.SILACC=1)
Byte 63Byte 62Byte 61…Byte 3Byte 2Byte 1Byte 0Page
CompDataDataCompDataDataCompDataDataCompDataData0
CompDataDataCompDataDataCompDataDataCompDataData1
CompDataDataCompDataDataCompDataDataCompDataData2
CompDataDataCompDataDataCompDataDataCompDataData3

The NVMCTRL automatically manages both scrambling and differential data storage if the tamper row resides in the secure Data Flash area and both are enabled (SECCTRL.DSCEN = 1 and SECCTRL.SILACC = 1).