EEPROM Registers
580
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Internal Memory
7.4.8 EEUNLOCK Register (Offset = 0x20) [reset = X]
EEPROM Unlock (EEUNLOCK)
The EEUNLOCK register can be used to unlock the whole EEPROM or a single block using a password.
Unlocking is only required if a password is registered using the EEPASSn registers for the block that is
selected by the EEBLOCK register. If block 0 has a password, it locks the remaining blocks from any type
of access, but uses its own protection mechanism, for example readable, but not writable when locked. In
addition, if block 0 has a password, it must be unlocked before unlocking any other block.
The EEUNLOCK register is written between 1 and 3 times to form the 32-bit, 64-bit, or 96-bit password
registered using the EEPASSn registers. The value used to configure the EEPASS0 register must always
be written last. For example, for a 96-bit password, the value used to configure the EEPASS2 register
must be written first followed by the EEPASS1 and EEPASS0 register values. The block or the whole
EEPROM can be re-locked by writing 0xFFFFFFFF to this register.
In the event that an invalid value is written to this register, the block remains locked. The state of the
EEPROM lock can be determined by reading back the EEUNLOCK register. If a multi-word password is
set and the number of words written is incorrect, writing 0xFFFFFFFF to this register reverts the EEPROM
lock to the locked state, and the proper unlock sequence can be retried.
Note that the internal logic is balanced to prevent any electrical or time-based attack being used to find the
correct password or its length.
NOTE:
A read of the EEUNLOCK register during the EEPROM initialization sequence is only valid
when the WORKING bit is 0 in EEDONE register:
EEUNLOCK is shown in
and described in
.
Return to
Figure 7-32. EEUNLOCK Register
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
UNLOCK
R/W-X
Table 7-33. EEUNLOCK Register Field Descriptions
Bit
Field
Type
Reset
Description
31-0
UNLOCK
R/W
X
EEPROM Unlock
The EEPROM is locked if the block referenced by the EEBLOCK
register has a password registered, or if the master block (block 0)
has a password.
Unlocking is performed by writing the password to this register.
The block or the EEPROM stays unlocked until it is locked again or
until the next reset.
It can be locked again by writing 0xFFFFFFFF to this register.
0x0 = The EEPROM is locked.
0x1 = The EEPROM is unlocked.