m29dw256g Numonyx, m29dw256g Datasheet - Page 22

• Manufacturer Part Number: m29dw256g
• Description: 256-mbit X16, Multiple Bank, Page, Dual Boot 3 V Supply Flash Memory
• Manufacturer: Numonyx

Note:
5.3
Note:
22/84
1
2
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.
Refer to
There is no means to verify the password after it is set. If the password is lost after setting
the password mode lock bit, there is no way to clear the NVPB lock bit.
Prior to entering the password protection mode, it is necessary to set a 64-bit password
and to verify it (see
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
programmed it cannot be erased, the device permanently remains in password
protection mode, and the 64-bit password can neither be retrieved nor reprogrammed.
Moreover, all commands to the address where the password is stored, are disabled.
Refer to
details on the block protection scheme.
Section 6.4.5
Section 6.4.6
Table 9: Block protection status
for a description of the NVPB lock bit command set.
for a description of the password protection mode command set.
Password protection mode command set on page
and
Figure 5: Software protection scheme
43). Password
for