A d v a n c e I n f o r m a t i o n
Secured Silicon Sector Flash Memory Region
The Secured Silicon Sector feature provides a 256 byte Flash memory region that enables per-
manent part identification through an Electronic Serial Number (ESN). The Secured Silicon Sector
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.
Spansion offers the device with the Secured Silicon Sector either factory locked or customer lock-
able. 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. The customer-lockable version is
shipped with the Secured Silicon Sector unprotected, allowing customers to utilize the that sector
in any manner they choose. The customer-lockable version has the Secured Silicon Sector Indi-
cator Bit permanently set to a 0. Thus, the Secured Silicon Sector Indicator Bit prevents
customer-lockable devices from being used to replace devices that are factory locked.
The system accesses the Secured Silicon Sector through a command sequence (see Enter Se-
cured Silicon Sector/Exit Secured Silicon Sector Command Sequence on page 32). After the
system writes the Enter Secured Silicon Sector command sequence, it may read the Secured Sil-
icon Sector by using the addresses normally occupied by the boot sectors. This mode of operation
continues until the system issues the Exit Secured Silicon Sector command sequence, or until
power is removed from the device. On power-up, or following a hardware reset, the device reverts
to sending commands to the boot sectors.
Factory Locked: Secured Silicon Sector Programmed
and Protected at the Factory
In a factory locked device, the Secured Silicon Sector is protected when the device is shipped from
the factory. The Secured Silicon Sector cannot be modified in any way. The device is available pre-
programmed with one of the following:
A random, secure ESN only
Customer code through the ExpressFlash service
Both a random, secure ESN and customer code through the ExpressFlash service.
In devices that have an ESN, a Bottom Boot device has the 16-byte (8-word) ESN in sector 0 at
addresses 00000h–0000Fh in byte mode (or 00000h–00007h in word mode). In the Top Boot de-
vice the ESN is in sector 70 at addresses 3FFF00h–3FFF0Fh in byte mode (or 1FFF80h–1FFF87h
in word mode). In the Uniform device the ESN is in sector 63 at addresses 3FFF00h-3FFF0Fh in
byte mode (or 1FFF80h-1FFF87h in word mode).
Customers may opt to have their code programmed by Spansion through the Spansion Express-
Flash service. Spansion programs the customer’s code, with or without the random ESN. The
devices are then shipped from the Spansion factory with the Secured Silicon Sector permanently
locked. Contact a Spansion representative for details on using the Spansion ExpressFlash service.
Customer Lockable: Secured Silicon Sector NOT Programmed
or Protected at the Factory
The customer lockable version allows the Secured Silicon Sector to be programmed once and then
permanently locked after it ships from Spansion. Note that the accelerated programming (ACC)
and unlock bypass functions are not available when programming the Secured Silicon Sector.
The Secured Silicon Sector area can be protected using the following procedures:
Write the three-cycle Enter Secured Silicon Region command sequence, and then follow the
in-system sector protect algorithm as shown in Figure 2, on page 25, except that RESET#
may be at either V or V . This allows in-system protection of the Secured Silicon Sector
IH
ID
26
S29AL032D
S29AL032D_00_A3 June 13, 2005
SPANSION [ SPANSION ]
