256Mb: 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.
LOCK REGISTER Commands
The ENTER LOCK REGISTER COMMAND SET (40h) command enables execution of all
READ or PROGRAM LOCK REGISTER commands. PROGRAM LOCK REGISTER (A0h)
configures the lock register, and READ LOCK REGISTER reads/confirms programmed
data.
PASSWORD PROTECTION Commands
The ENTER PASSWORD PROTECTION COMMAND SET (60h) command enables execu-
tion of password protection commands. PROGRAM PASSWORD (A0h) programs the 64-
bit password used in the password protection mode. To program the 64-bit password in
8-bit mode, the complete command sequence must be entered eight times at eight con-
secutive addresses selected by A[1:0] plus DQ15/A-1; in 16-bit mode, the command se-
quence must be entered four times at four consecutive addresses selected by A[1:0]. By
default, all password bits are set to 1. The password can be checked by issuing a READ
PASSWORD command.
READ PASSWORD verifies the password used in password protection mode. To verify
the 64-bit password in 8-bit mode, the complete command sequence must be entered
eight times at eight consecutive addresses selected by A[1:0] plus DQ15/A-1. In 16-bit
mode, the command sequence must be entered four times at four consecutive address-
es selected by A[1:0]. If the password mode lock bit is programmed and a user attempts
to read the password, the device outputs FFh.
UNLOCK PASSWORD (25/03h) clears the nonvolatile protection bit lock bit, allowing
the nonvolatile protection bits to be modified. UNLOCK PASSWORD must be issued
with the correct password and requires a 1μs delay between successive UNLOCK PASS-
WORD commands. The delay helps prevent password intruders from trying all possible
64-bit combinations. If the delay does not occur, the latest command is ignored. After a
valid 64-bit password is entered, approximately 1μs is required to unlock the device.
NONVOLATILE PROTECTION Commands
The ENTER NONVOLATILE PROTECTION COMMAND SET (C0h) command enables
nonvolatile protection mode commands to be issued to the device. A block can be pro-
tected from program or erase operations using a PROGRAM NONVOLATILE PROTEC-
TION BIT (A0h) command, along with the block address. This command sets the non-
volatile protection bit to 0 for a given block.
The status of a nonvolatile protection bit for a given block or group of blocks can be
read using a READ NONVOLATILE MODIFY PROTECTION BIT command, along with
the block address. The nonvolatile protection bits are erased simultaneously using a
CLEAR ALL NONVOLATILE PROTECTION BITS (80/30h) command. No specific block
address is required. If the nonvolatile protection bit lock bit is set to 0, the command
fails.
PDF: 09005aef84bd3b68
m29w_256mb.pdf - Rev. B 5/13 EN
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