M25PE16 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'M25PE16' PDF : 56 Pages View PDF
M25PE16
Operating features
4.8.2
Specific Hardware and Software protections
There are two Software Protected modes, SPM1 and SPM2, that can be combined to
protect the memory array as required. The SPM2 can be Hardware protected with the help
of the W input pin.
SPM1 and SPM2
● The first Software Protected mode (SPM1) is managed by specific Lock Registers
assigned to each 64 Kbyte sector.
The Lock Registers can be read and written using the Read Lock Register (RDLR) and
Write to Lock Register (WRLR) instructions.
In each Lock Register two bits control the protection of each sector: the Write Lock Bit
and the Lock Down Bit.
– Write Lock Bit:
The Write Lock Bit determines whether the contents of the sector can be modified
(using the Write, Program or Erase instructions). When the Write Lock Bit is set,
‘1’, the sector is write protected – any operations that attempt to change the data
in the sector will fail. When the Write Lock Bit is reset to ‘0’, the sector is not write
protected by the Lock Register, and may be modified.
– Lock Down Bit:
The Lock Down Bit provides a mechanism for protecting software data from simple
hacking and malicious attack. When the Lock Down Bit is set, ‘1’, further
modification to the Write Lock and Lock Down Bits cannot be performed. A reset,
or power-up, is required before changes to these bits can be made. When the
Lock Down Bit is reset, ‘0’, the Write Lock and Lock Down Bits can be changed.
The Write Lock Bit and the Lock Down Bit are volatile and their value is reset to ‘0’ after
a Power-Down or a Reset (see Table 12: Device status after a RESET Low pulse).
The definition of the Lock Register bits is given in Table 9: Lock Register out.
Table 2. Software protection truth table (Sectors 0 to 31, 64 Kbyte granularity)
Sector Lock
Register
Lock
Write
Down Bit Lock Bit
Protection Status
0
0
Sector Unprotected from Program/Erase/Write operations, Protection Status
Reversible
0
1
Sector Protected from Program/Erase/Write operations, Protection Status
Reversible
1
0
Sector Unprotected from Program/Erase/Write operations,
Sector Protection Status cannot be changed except by a Reset or Power-up.
1
1
Sector Protected from Program/Erase/Write operations,
Sector Protection Status cannot be changed except by a Reset or Power-up.
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