Numonyx™ StrataFlash® Embedded Memory (P33)
11.4.5
11.4.6
Security Modes
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.
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 11.3.6, “Program Protection” on
page 62 and Section 11.4.4, “Erase Protection” on page 63).
The Numonyx™ StrataFlash® Embedded Memory (P33) device also offers four pre-
defined areas in the main array that can be configured as One-Time Programmable
(OTP) for the highest level of security. These include the four 32 KB parameter blocks
together as one and the three adjacent 128 KB main blocks. This is available for top or
bottom parameter devices.
11.4.6.1
Lock Block
To lock a block, issue the Lock Block Setup command. The next command must be the
Lock Block command issued to the desired block’s address (see Section 9.6, “Device
Command Bus Cycles” on page 44 and Figure 39, “Block Lock Operations Flowchart” on
page 75). If the Set 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
.
11.4.6.2
11.4.6.3
Unlock Block
The Unlock Block command is used to unlock blocks (see Section 9.6, “Device
Command Bus Cycles” on page 44). 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 31, “Block Locking State Diagram” on page 65).
Lock-Down Block
A locked or unlocked block can be locked-down by writing the Lock-Down Block
command sequence (see Section 9.6, “Device Command Bus Cycles” on page 44).
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 Unlock
Block command with WP# deasserted. To return an unlocked block to locked-down
state, a 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 31, “Block Locking State Diagram” on page 65).
Datasheet
64
November 2007
Order Number: 314749-05
NUMONYX [ NUMONYX B.V ]
