AM29PDL640G datasheet(19/61 Pages) AMD

19 / 61 page

December 13, 2005

Am29PDL640G

D A TA SH EE T

SECTOR PROTECTION

The Am29PDL640G features several levels of sector

protection, which can disable both the program and

erase operations in certain sectors or sector groups:

Persistent Sector Protection

A command sector protection method that replaces

the old 12 V controlled protection method.

Password Sector Protection

A highly sophisticated protection method that requires

a password before changes to certain sectors or sec-

tor groups are permitted

WP# Hardware Protection

A write protect pin that can prevent program or erase

operations in sectors 0, 1, 140, and 141.

All parts default to operate in the Persistent Sector

Protection mode. The customer must then choose if

the Persistent or Password Protection method is most

desirable. There are two one-time programmable

non-volatile bits that define which sector protection

method will be used. If the Persistent Sector Protec-

tion method is desired, programming the Persistent

Sector Protection Mode Locking Bit permanently

sets the device to the Persistent Sector Protection

mode. If the Password Sector Protection method is de-

sired, programming the Password Mode Locking Bit

permanently sets the device to the Password Sector

Protection mode. It is not possible to switch between

the two protection modes once a locking bit has been

set. One of the two modes must be selected when

the device is first programmed. This prevents a pro-

gram or virus from later setting the Password Mode

Locking Bit, which would cause an unexpected shift

from the default Persistent Sector Protection Mode

into the Password Protection Mode.

The WP# Hardware Protection feature is always avail-

able, independent of the software managed protection

method chosen.

The device is shipped with all sectors unprotected.

AMD offers the option of programming and protecting

sectors at the factory prior to shipping the device

through AMD’s ExpressFlash™ Service. Contact an

AMD representative for details.

It is possible to determine whether a sector is pro-

tected or unprotected. See Autoselect Mode for de-

tails.

Persistent Sector Protection

The Persistent Sector Protection method replaces the

12 V controlled protection method in previous AMD

flash devices. This new method provides three differ-

ent sector protection states:

■ Persistently Locked—The sector is protected and

cannot be changed.

■ Dynamically Locked—The sector is protected and

can be changed by a simple command.

■ Unlocked—The sector is unprotected and can be

changed by a simple command.

To achieve these states, three types of “bits” are used:

Persistent Protection Bit (PPB)

A single Persistent (non-volatile) Protection Bit is as-

signed to a maximum four sectors (see the sector ad-

dress tables for specific sector protection groupings).

All 4 Kword boot-block sectors have individual sector

Persistent Protection Bits (PPBs) for greater flexibility.

Each PPB is individually modifiable through the PPB

Write Command.

The device erases all PPBs in parallel. If any PPB re-

quires erasure, the device must be instructed to pre-

program all of the sector PPBs prior to PPB erasure.

Otherwise, a previously erased sector PPBs can po-

tentially be over-erased. The flash device does not

have a built-in means of preventing sector PPBs

over-erasure.

Persistent Protection Bit Lock (PPB Lock)

The Persistent Protection Bit Lock (PPB Lock) is a glo-

bal volatile bit. When set to “1”, the PPBs cannot be

changed. When cleared (“0”), the PPBs are change-

able. There is only one PPB Lock bit per device. The

PPB Lock is cleared after power-up or hardware reset.

There is no command sequence to unlock the PPB

Lock.

Dynamic Protection Bit (DYB)

A volatile protection bit is assigned for each sector.

After power-up or hardware reset, the contents of all

DYBs is “0”. Each DYB is individually modifiable

through the DYB Write Command.

When the par ts are first shipped, the PPBs are

cleared, the DYBs are cleared, and PPB Lock is de-

faulted to power up in the cleared state – meaning the

PPBs are changeable.

When the device is first powered on the DYBs power

up cleared (sectors not protected). The Protection

State for each sector is determined by the logical OR

of the PPB and the DYB related to that sector. For the

sectors that have the PPBs cleared, the DYBs control

whether or not the sector is protected or unprotected.

By issuing the DYB Write command sequences, the

DYBs will be set or cleared, thus placing each sector in

the protected or unprotected state. These are the

so-called Dynamic Locked or Unlocked states. They

are called dynamic states because it is very easy to

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