S71GS256 datasheet(54/195 Pages) SPANSION

54 / 195 page

S29GLxxxN MirrorBitTM Flash Family

S29GLxxxN_MCP_A1 December 15, 2004

Advan ce

In form ati o n

using the Persistent Sector Protection method, they must set the Persistent

Sector Protection Mode Locking Bit. This will permanently set the part to op-

erate only using Persistent Sector Protection. If the customer decides to use the

password method, they must set the Password Mode Locking Bit. This will

permanently set the part to operate only using password sector protection.

It is important to remember that setting either the Persistent Sector Protec-

tion Mode Locking Bit or the Password Mode Locking Bit permanently

selects the protection mode. It is not possible to switch between the two methods

once a locking bit has been set. It is important that one mode is explicitly

selected when the device is first programmed, rather than relying on the

default mode alone. This is so that it is not possible for a system program or

virus to later set the Password Mode Locking Bit, which would cause an unex-

pected shift from the default Persistent Sector Protection Mode into the Password

Protection Mode.

The device is shipped with all sectors unprotected. The factory offers the option

of programming and protecting sectors at the factory prior to shipping the device

through the ExpressFlash™ Service. Contact your sales representative for details.

It is possible to determine whether a sector is protected or unprotected. See “Au-

toselect Command Sequence” section on page 66 for details.

Advanced Sector Protection

Advanced Sector Protection features several levels of sector protection, which can

disable both the program and erase operations in certain sectors.

Persistent Sector Protection is a method that replaces the old 12V controlled

protection method.

Password Sector Protection is a highly sophisticated protection method that

requires a password before changes to certain sectors are permitted.

Lock Register

The Lock Register consists of 3 bits (DQ2, DQ1, and DQ0). These DQ2, DQ1, DQ0

bits of the Lock Register are programmable by the user. Users are not allowed to

program both DQ2 and DQ1 bits of the Lock Register to the 00 state. If the user

tries to program DQ2 and DQ1 bits of the Lock Register to the 00 state, the device

will abort the Lock Register back to the default 11 state. The programming time

of the Lock Register is same as the typical word programming time without uti-

lizing the Write Buffer of the device. During a Lock Register programming

sequence execution, the DQ6 Toggle Bit I will toggle until the programming of the

Lock Register has completed to indicate programming status. All Lock Register

bits are readable to allow users to verify Lock Register statuses.

The Customer Secured Silicon Sector Protection Bit is DQ0, Persistent Protection

Mode Lock Bit is DQ1, and Password Protection Mode Lock Bit is DQ2 are acces-

sible by all users. Each of these bits are non-volatile. DQ15-DQ3 are reserved and

must be 1's when the user tries to program the DQ2, DQ1, and DQ0 bits of the

Lock Register. The user is not required to program DQ2, DQ1 and DQ0 bits of the

Lock Register at the same time. This allows users to lock the Secured Silicon Sec-

tor and then set the device either permanently into Password Protection Mode or

Persistent Protection Mode and then lock the Secured Silicon Sector at separate

instances and time frames.

Secured Silicon Sector Protection allows the user to lock the Secured Silicon

Sector area

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