256Mb: 3V Embedded Parallel NOR Flash
Protection Operations
The READ NONVOLATILE PROTECTION BIT LOCK BIT STATUS command is used to
read the status of the nonvolatile protection bit lock bit.
VOLATILE PROTECTION Commands
After the ENTER VOLATILE PROTECTION COMMAND SET (E0h) command has been
issued, commands related to the volatile protection mode can be issued to the device.
This command requires three bus write cycles.
The PROGRAM VOLATILE PROTECTION BIT (A0h) command individually sets a vola-
tile protection bit to 0 for a given block. If the nonvolatile protection bit for the same
block is set, the block is locked regardless of the value of the volatile protection bit. (See
the Block Protection Status table.)
The status of a volatile protection bit for a given block can be read by issuing a READ
VOLATILE PROTECTION BIT STATUS command along with the block address.
The CLEAR VOLATILE PROTECTION BIT (A0h) command individually clears (sets to 1)
the volatile protection bit for a given block. If the nonvolatile protection bit for the same
block is set, the block is locked regardless of the value of the volatile protection bit. (See
the Block Protection Status table.)
EXTENDED MEMORY BLOCK Commands
The device has one extra 256-word block (extended memory block) that can only be ac-
cessed by the ENTER EXTENDED MEMORY BLOCK command when the device is in ex-
tended block mode. The device can be shipped with the extended memory block pre-
locked permanently by Micron, or with the extended memory block unlocked, enabling
customers to permanently program and lock it. (See Lock Register, the AUTO SELECT
command, and the Block Protection table.)
The extended memory block is used as a security block (to provide a permanent securi-
ty identification number) or to store additional information. The extended memory
block is divided in two memory areas of 128 words each:
The first area is factory locked and the second one is customer lockable. It is perma-
nently protected from program operations and cannot be unprotected. The random
number, electronic serial number (ESN) and security identification number are written
in this section in the factory.
The second area is customer lockable. It is up to the customer to protect it from pro-
gram operations. Its status is indicated by bit DQ6 and DQ7. When DQ7 is set to 1 and
DQ6 to 0, it indicates that this second memory area is customer lockable. When DQ7
and DQ6 are both set to 1, it indicates that the second part of the extended memory
block is customer locked and protected from program operations. Bits DQ6 and DQ7
are the most significant bits in the extended block protection indicator and a specific
procedure must be followed to read it.
Table 18: Extended Memory Block Address and Data
Data
Address
Micron prelocked
Secure ID number
Unavailable
Customer Lockable
Unavailable
000000h–00007Fh
000080h-0000FFh
Determined by customer
PDF: 09005aef84ecabef
m29dw_256g.pdf - Rev. A 10/12 EN
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