AM29PDL640AGA85NS SPANSION [SPANSION], AM29PDL640AGA85NS Datasheet - Page 18

• Manufacturer Part Number: AM29PDL640AGA85NS
• Description: 64 Megabit (4 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 16 Mbit (1 M x 16-Bit) Pseudo Static RAM
• Manufacturer: SPANSION [SPANSION]

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:
16
P R E L I M I N A R Y
Am49PDL640AG
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
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.
November 20, 2003