JS28F256P33BFE datasheet(30/90 Pages) MICRON

30 / 90 page

P33-65nm

Datasheet

Aug 2009

Order Number: 320003-08

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 27 and Section 9.5, “Erase Protection” on page 29).

The P33-65nm 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.

10.1.1

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 6.2, “Device

Command Bus Cycles” on page 18 and Figure 36, “Block Lock Operations Flowchart” on

page 77). 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.

10.1.2

Unlock Block

The Unlock Block command is used to unlock blocks (see Section 6.2, “Device

Command Bus Cycles” on page 18). 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 8, “Block Locking State Diagram” on page 31).

10.1.3

Lock-Down Block

A locked or unlocked block can be locked-down by writing the Lock-Down Block

command sequence (see Section 6.2, “Device Command Bus Cycles” on page 18).

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 8,

“Block Locking State Diagram” on page 31).

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