256Mb: 3V Embedded Parallel NOR Flash
Protection Operations
1μs delay between successive UNLOCK PASSWORD commands in order to prevent un-
authorized intruders from retrieving the password by trying all possible 64-bit combi-
nations. 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 provi-
ded.
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. This command requires three bus write cycles.
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. This command must be used ac-
cording to all program command timings. Command results can be verified by checking
the status register.
The status of a nonvolatile protection bit for a given block or group of blocks can be
read by issuing a READ NONVOLATILE MODIFY PROTECTION BIT command, along
with the block address.
The nonvolatile protection bits are erased simultaneously by issuing a CLEAR ALL
NONVOLATILE PROTECTION BITS (80/30h) command. No specific block address is re-
quired. If the nonvolatile protection bit lock bit is set to 0, the command fails.
PDF: 09005aef84ecabef
m29dw_256g.pdf - Rev. A 10/12 EN
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