306666-11 Datasheet, PDF (64/99 Pages) Numonyx B.V – Numonyx StrataFlash Embedded Memory

P30
13.0
13.1
13.1.1
13.1.2
13.1.3
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, V_PP data security can be used to
inhibit program and erase operations (see Section 11.6, “Program Protection” on
page 61 and Section 12.4, “Erase Protection” on page 63).
The P30 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.
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 9.2, “Device Commands” on page 45 and
Figure 44, “Block Lock Operations Flowchart” on page 85). 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 V_PP. The block
lock bits may be modified and/or read even if V_PP is at or below V_PPLK.
Unlock Block
The Unlock Block command is used to unlock blocks (see Section 9.2, “Device
Commands” on page 45). 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 30, “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 9.2, “Device Commands” on page 45). 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 V_IL. Locked-down blocks revert to
the locked state upon reset or power up the device (see Figure 30, “Block Locking State
Diagram” on page 65).
Datasheet
64
November 2007
Order Number: 306666-11