P30-65nm SBC
10.0
Security
The device features security modes used to protect the information stored in the flash
memory array. The following sections describe each security mode in detail.
10.1
Block Locking
Individual instant block locking is used to protect user code and/or data within the flash
memory array. All blocks power up in a locked state to protect array data from being
altered during power transitions. Any block can be locked or unlocked with no latency.
Locked blocks cannot be programmed or erased; they can only be read.
Software-controlled security is implemented using the Block Lock and Block Unlock
commands. Hardware-controlled security can be implemented using the Block Lock-
Down command along with asserting WP#. Also, VPP data security can be used to
inhibit program and erase operations (see Section 8.6, “Program Protection” on
page 28 and Section 9.5, “Erase Protection” on page 30).
10.1.1
Lock Block
To lock a block, issue the Block Lock Setup command. The next command must be the
Block Lock command issued to the desired block’s address (see Section 6.2, “Device
Command Bus Cycles” on page 20 and Figure 39, “Block Lock Operations Flowchart” on
page 80). If the Configure Read Configuration Register command is issued after the
Block Lock Setup command, the device configures the RCR instead.
Block lock and unlock operations are not affected by the voltage level on VPP. The block
lock bits may be modified and/or read even if VPP is at or below VPPLK
.
10.1.2
10.1.3
Unlock Block
The Block Unlock command is used to unlock blocks (see Section 6.2, “Device
Command Bus Cycles” on page 20). Unlocked blocks can be read, programmed, and
erased. Unlocked blocks return to a locked state when the device is reset or powered
down. If a block is in a lock-down state, WP# must be deasserted before it can be
unlocked (see Figure 9, “Block Locking State Diagram” on page 32).
Lock-Down Block
A locked or unlocked block can be locked-down by writing the Block Lock-Down
command sequence (see Section 6.2, “Device Command Bus Cycles” on page 20).
Blocks in a lock-down state cannot be programmed or erased; they can only be read.
However, unlike locked blocks, their locked state cannot be changed by software
commands alone. A locked-down block can only be unlocked by issuing the Block
Unlock command with WP# deasserted. To return an unlocked block to locked-down
state, a Block Lock-Down command must be issued prior to changing WP# to VIL.
Locked-down blocks revert to the locked state upon reset or power up the device (see
Figure 9, “Block Locking State Diagram” on page 32).
10.1.4
Block Lock Status
The Read Device Identifier command is used to determine a block’s lock status (see
Section 7.2, “Read Device Identifier” on page 22). Data bits DQ[1:0] display the
addressed block’s lock status; DQ0 is the addressed block’s lock bit, while DQ1 is the
addressed block’s lock-down bit.
Datasheet
31
Apr 2010
OrderNumber:208033-02
MICRON [ MICRON TECHNOLOGY ]
