32Mb, 64Mb, 128Mb: 3V Embedded Parallel NOR Flash
Protection Operations
Protection Operations
Blocks can be protected individually against accidental PROGRAM, ERASE, or READ op-
erations on both 8-bit and 16-bit configurations. The block protection scheme is shown
in the Software Protection Scheme figure.
Memory block and extended memory block protection is configured through the lock
register (see Lock Register section).
LOCK REGISTER Commands
After the ENTER LOCK REGISTER COMMAND SET (40h) command has been issued, all
bus READ or PROGRAM operations can be issued to the lock register.
The PROGRAM LOCK REGISTER (A0h) command allows the lock register to be config-
ured. The programmed data can then be checked with a READ LOCK REGISTER com-
mand by driving CE# and OE# LOW with the appropriate address data on the address
bus.
PASSWORD PROTECTION Commands
After the ENTER PASSWORD PROTECTION COMMAND SET (60h) command has been
issued, the commands related to password protection mode can be issued to the device.
The PROGRAM PASSWORD (A0h) command is used to program the 64-bit password
used in the password protection mode. To program the 64-bit password, the complete
command sequence must be entered eight times at eight consecutive addresses selec-
ted by A[1:0] plus DQ15/A-1 in 8-bit mode, or four times at four consecutive addresses
selected by A[1:0] in 16-bit mode. By default, all password bits are set to 1. The password
can be checked by issuing a READ PASSWORD command.
The READ PASSWORD command is used to verify the password used in password pro-
tection mode. To verify the 64-bit password, the complete command sequence must be
entered eight times at eight consecutive addresses selected by A[1:0] plus DQ15/A-1 in
8-bit mode, or four times at four consecutive addresses selected by A[1:0] in 16-bit
mode. If the password mode lock bit is programmed and the user attempts to read the
password, the device will output FFh onto the I/O data bus.
The UNLOCK PASSWORD (25/03h) command is used to clear the nonvolatile protec-
tion bit lock bit, allowing the nonvolatile protection bits to be modified. The UNLOCK
PASSWORD command must be issued, along with the correct password, and requires a
1μs delay between successive UNLOCK PASSWORD commands in order to prevent
hackers from cracking the password by trying all possible 64-bit combinations. If this
delay does not occur, the latest command will be ignored. Approximately 1μs is required
for unlocking the device after the valid 64-bit password has been provided.
NONVOLATILE PROTECTION Commands
After the ENTER NONVOLATILE PROTECTION COMMAND SET (C0h) command has
been issued, the commands related to nonvolatile protection mode can be issued to the
device.
A block can be protected from program or erase by issuing a PROGRAM NONVOLATILE
PROTECTION BIT (A0h) command, along with the block address. This command sets
the nonvolatile protection bit to 0 for a given block.
PDF: 09005aef84dc44a7
m29ew_32Mb-128Mb.pdf - Rev. B 11/12 EN
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