256Mb, 512Mb, 1Gb, 2Gb: 3V Embedded Parallel NOR Flash
Device Protection
Device Protection
Hardware Protection
The V
PP
/WP# function provides a hardware method of protecting either the highest/
lowest block. When V
PP
/WP# is LOW, PROGRAM and ERASE operations on either of
these block options is ignored to provide protection. When V
PP
/WP# is HIGH, the de-
vice reverts to the previous protection status for the highest/lowest block or top/bottom
two blocks. PROGRAM and ERASE operations can modify the data in either of these
block options unless block protection is enabled.
Note:
Micron highly recommends driving V
PP
/WP# HIGH or LOW. If a system needs to
float the V
PP
/WP# pin, without a pull-up/pull-down resistor and no capacitor, then an
internal pull-up resistor is enabled.
Table 16: V
PP
/WP# Functions
V
PP
/WP# Settings
V
IL
V
IH
Function
Highest/lowest block is protected; for a 2Gb device, both the highest and the lowest blocks
are hardware-protected (block 0 and block 2047)
Highest/lowest block or the top/bottom two blocks are unprotected unless software pro-
tection is activated.
Software Protection
Four software protection modes are available:
•
•
•
•
Volatile protection
Nonvolatile protection
Password protection
Password access
The device is shipped with all blocks unprotected. On first use, the device defaults to
the nonvolatile protection mode but can be activated in either the nonvolatile protec-
tion or password protection mode.
The desired protection mode is activated by setting either the nonvolatile protection
mode lock bit or the password protection mode lock bit of the lock register (see the Lock
Register section). Both bits are one-time-programmable and nonvolatile; therefore, af-
ter the protection mode has been activated, it cannot be changed, and the device is set
permanently to operate in the selected protection mode. It is recommended that the
desired software protection mode be activated when first programming the device.
For the lowest and highest blocks, a higher level of block protection can be achieved by
locking the blocks using nonvolatile protection mode and holding V
PP
/WP# LOW.
Blocks with volatile protection and nonvolatile protection can coexist within the memo-
ry array. If the user attempts to program or erase a protected block, the device ignores
the command and returns to read mode.
The block protection status can be read by performing a read electronic signature or by
issuing an AUTO SELECT command (see the Block Protection table).
PDF: 09005aef849b4b09
m29ew_256mb_2gb.pdf - Rev. B 8/12 EN
45
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2012 Micron Technology, Inc. All rights reserved.
MICRON [ MICRON TECHNOLOGY ]
