32Mb, 64Mb, 128Mb: 3V Embedded Parallel NOR Flash
Device Protection
Device Protection
Hardware Protection
The VPP/WP# function provides a hardware method of protecting either the highest/
lowest block or the top/bottom two blocks. When VPP/WP# is LOW, PROGRAM and
ERASE operations on either of these block options is ignored to provide protection.
When VPP/WP# is HIGH, the device 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 VPP/WP# HIGH or LOW. If a system needs to
float the VPP/WP# pin, without a pull-up/pull-down resistor and no capacitor, then an
internal pull-up resistor is enabled.
Table 22: VPP/WP# Functions
VPP/WP# Settings
Function
VIL
Highest/lowest block or the top/bottom two blocks are protected.
VIH
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 or for the top/bottom two blocks, a higher level of
block protection can be achieved by locking the blocks using nonvolatile protection
mode and holding VPP /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: 09005aef84dc44a7
m29ew_32Mb-128Mb.pdf - Rev. B 11/12 EN
Micron Technology, Inc. reserves the right to change products or specifications without notice.
55
© 2012 Micron Technology, Inc. All rights reserved.
MICRON [ MICRON TECHNOLOGY ]
