s71gl128nc0 Meet Spansion Inc., s71gl128nc0 Datasheet - Page 60

• Manufacturer Part Number: s71gl128nc0
• Description: Stacked Multi-chip Product Mcp 512/256/128 Megabit 32/16/8 M X 16-bit Cmos 3.0 Volt-only Mirrorbittm Page-mode Flash Memory With 64 Megabit 4m X 16-bit Psram
• Manufacturer: Meet Spansion Inc.

60
64-bit Password
Persistent Protection Bit Lock (PPB Lock Bit)
Secured Silicon Sector Flash Memory Region
programmed, the Persistent Protection Mode Lock Bit is disabled from program-
ming, guaranteeing that no changes to the protection scheme are allowed.
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.
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.
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.
S29GLxxxN MirrorBit
A d v a n c e
TM
Flash Family
I n f o r m a t i o n
S29GLxxxN_MCP_A1 December 15, 2004