256Mb: 3V Embedded Parallel NOR Flash
Protection Operations
pair continue the pattern shown in the table as follows: address and data = 02 and
PWD2; 03 and PWD3.
10. Both nonvolatile and volatile protection bit settings are as follows: Protected state = 00;
Unprotected state= 01.
11. The CLEAR ALL NONVOLATILE PROTECTION BITS command programs all nonvolatile pro-
tection bits before erasure. This prevents over-erasure of previously cleared nonvolatile
protection bits.
Protection Operations
Blocks can be protected individually against accidental PROGRAM and ERASE opera-
tions. 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) requires three bus write cycles. Af-
ter it has been issued, all bus READ or PROGRAM operations can be issued to the lock
register.
The EXIT PROTECTION COMMAND SET (90/00h) command must be used to exit the
lock register ane return to read mode.
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, only commands related to password protection mode and the EXIT PROTEC-
TION COMMAND SET command can be issued to the device. This command requires
three bus write cycles. The EXIT PROTECTION COMMAND SET command must be is-
sued following all password protection commands to return the device to read mode.
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 four times at four consecutive addresses selected
by A[1:0] in 16-bit mode. This command must be used according to all program com-
mand timings. Command results can be verified by checking the status register. By de-
fault, 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 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
PDF: 09005aef84ecabef
m29dw_256g.pdf - Rev. A 10/12 EN
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