JS28F256P30B95A datasheet(37/97 Pages) MICRON

37 / 97 page

August 2008

Datasheet

Order Number: 306666-12

P30

10.0

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.

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 8.7, “Program Protection” on

page 34 and Section 9.4, “Erase Protection” on page 36).

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.

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 6.0, “Command Set” on page 24 and Figure 40,

“Block Lock Operations Flowchart” on page 86). 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 6.0, “Command Set”

on page 24). 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 12,

“Block Locking State Diagram” on page 38).

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 6.0, “Command Set” on page 24). 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 12, “Block Locking State

Diagram” on page 38).

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