TM4C1231H6PGE Datasheet, PDF (541/1192 Pages) Texas Instruments – Tiva™ TM4C1231H6PGE Microcontroller

Tiva^™ TM4C1231H6PGE Microcontroller
Register 20: EEPROM Unlock (EEUNLOCK), offset 0x020
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 0xFFFF.FFFF 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 0xFFFF.FFFF 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.
EEPROM Unlock (EEUNLOCK)
Base 0x400A.F000
Offset 0x020
Type RW, reset -
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
UNLOCK
Type RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
Reset
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
UNLOCK
Type RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
Reset
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Bit/Field
31:0
Name
UNLOCK
Type
RW
Reset
-
Description
EEPROM Unlock
Value Description
0 The EEPROM is locked.
1 The EEPROM is unlocked.
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
0xFFFF.FFFF to this register.
June 12, 2014
541
Texas Instruments-Production Data