S71GS256 datasheet(59/195 Pages) SPANSION

59 / 195 page

December 15, 2004 S29GLxxxN_MCP_A1

S29GLxxxN MirrorBitTM Flash Family

Ad vance

Info rmat i o n

programmed, the Persistent Protection Mode Lock Bit is disabled from program-

ming, guaranteeing that no changes to the protection scheme are allowed.

64-bit Password

The 64-bit Password is located in its own memory space and is accessible through

the use of the Password Program and Password Read commands. The password

function works in conjunction with the Password Protection Mode Lock Bit, which

when programmed, prevents the Password Read command from reading the con-

tents of the password on the pins of the device.

Persistent Protection Bit Lock (PPB Lock Bit)

A global volatile bit. The PPB Lock Bit is a volatile bit that reflects the state of the

Password Protection Mode Lock Bit after power-up reset. If the Password Protec-

tion Mode Lock Bit is also programmed after programming the Password, the

Password Unlock command must be issued to clear and unfreeze the PPB Lock Bit

after a hardware reset (RESET# asserted) or a power-up reset. Successful exe-

cution of the Password Unlock command clears and unfreezes the PPB Lock Bit,

allowing for sector PPB bits to be modified. Without issuing the Password Unlock

command, while asserting RESET#, taking the device through a power-on reset,

or issuing the PPB Lock Bit Set command sets the PPB Lock Bit to a the “freeze

state”.

If the Password Protection Mode Lock Bit is not programmed, the device defaults

to Persistent Protection Mode. In the Persistent Protection Mode, the PPB Lock Bit

is cleared to the “unfreeze state” after power-up or hardware reset. The PPB Lock

Bit is set to the “freeze state” by issuing the PPB Lock Bit Set command. Once set

to the “freeze state” the only means for clearing the PPB Lock Bit to the “unfreeze

state” is by issuing a hardware or power-up reset. The Password Unlock com-

mand is ignored in Persistent Protection Mode.

Reading the PPB Lock Bit requires a 200ns access time.

Secured Silicon Sector Flash Memory Region

The Secured Silicon Sector feature provides a Flash memory region that enables

permanent part identification through an Electronic Serial Number (ESN). The

Secured Silicon Sector is 256 bytes in length, and uses a Secured Silicon Sector

Indicator Bit (DQ7) to indicate whether or not the Secured Silicon Sector is locked

when shipped from the factory. This bit is permanently set at the factory and can-

not be changed, which prevents cloning of a factory locked part. This ensures the

security of the ESN once the product is shipped to the field.

The factory offers the device with the Secured Silicon Sector either customer

lockable (standard shipping option) or factory locked (contact an AMD sales rep-

resentative for ordering information). The customer-lockable version is shipped

with the Secured Silicon Sector unprotected, allowing customers to program the

sector after receiving the device. The customer-lockable version also has the Se-

cured Silicon Sector Indicator Bit permanently set to a “0.” The factory-locked

version is always protected when shipped from the factory, and has the Secured

Silicon Sector Indicator Bit permanently set to a “1.” Thus, the Secured Silicon

Sector Indicator Bit prevents customer-lockable devices from being used to re-

place devices that are factory locked. Note that the ACC function and unlock

bypass modes are not available when the Secured Silicon Sector is enabled.

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