M29DW128G70NF6E NUMONYX, M29DW128G70NF6E Datasheet - Page 22

• Manufacturer Part Number: M29DW128G70NF6E
• Description: P7ED TSOP56 DUAL BANK
• Manufacturer: NUMONYX

Software protection
Note:
6.2.2
Note:
6.3
22/85
1
2
2
1
If one of the non-volatile protected blocks needs to be unprotected (corresponding NVPB
set to ‘1’), a few more steps are required:
1.
2.
3.
To achieve the best protection, it is recommended to execute the NVPB Lock Bit Program
command early in the boot code and to protect the boot code by holding V
The NVPBs and VPBs have the same function when V
when V
Refer to
details on the block protection mechanism, and to
volatile protection mode command set.
Non-volatile protection bit lock bit
The non-volatile protection bit lock bit (NVPB lock bit) is a global volatile bit for all blocks.
When set (programmed to ‘0’), it prevents changing the state of the NVPBs. When cleared
(programmed to ‘1’), the NVPBs can be set and reset using the NVPB Program command
and Clear all NVPBs command, respectively.
There is only one NVPB lock bit per device.
Refer to
No software command unlocks this bit unless the device is in password protection mode; it
can be cleared only by taking the device through a hardware reset or a power-up.
The NVPB lock bit must be set (programmed to ‘0’) only after all NVPBs are configured to
the desired settings.
Password protection mode
The password protection mode provides an even higher level of security than the non-
volatile protection mode by requiring a 64-bit password for unlocking the device NVPB lock
bit.
In addition to this password requirement, the NVPB lock bit is set ‘0’ after power-up and
reset to maintain the device in password protection mode. Successful execution of the
Password Unlock command by entering the correct password clears the NVPB lock bit,
allowing for block NVPBs to be modified.
If the password provided is not correct, the NVPL Lock bit remains locked and the state of
the NVPBs cannot be modified.
To place the device in password protection mode, the following steps are required:
1.
2.
First, the NVPB lock bit must be cleared by either putting the device through a power
cycle, or hardware reset
The NVPBs can then be changed to reflect the desired settings
The NVPB lock bit must be set once again to lock the NVPBs. The device operates
normally again.
Prior to entering the password protection mode, it is necessary to set a 64-bit password
and to verify it (see
Password verification is only allowed during the password programming operation
The password protection mode is then activated by programming the password
protection mode lock bit to ‘0’. This operation is not reversible and once the bit is
PP
Table 14: Block protection status
Section 7.3.6
/WP pin is at the voltage for program acceleration (V
for a description of the NVPB lock bit command set.
Password Program command
and
Figure 5: Software protection scheme
Section 7.3.5
PP
and
/WP pin is High, V
Password Read
PPH
for a description of the non-
).
PP
IH
command).
/WP Low, V
, as they do
M29DW128G
for
IL
.