S29AS008J datasheet(23/55 Pages) SPANSION

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November 9, 2011 S29AS008J_00_09

S29AS008J

Data

She e t

Secured Silicon Sector Flash Memory Region

The Secured Silicon Sector feature provides a 256-byte Flash memory region that enables permanent 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 cannot 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-lockable. 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 group unprotected, allowing customers to utilize the that sector in any manner they choose. The

customer-lockable version has the Secured Silicon Sector Indicator 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 Secured Silicon

Sector/Exit Secured Silicon Sector Command Sequence on page 29). After the system writes the Enter

Secured Silicon Sector command sequence, it may read the Secured Silicon 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.

8.1

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 device, the ESN is in

sector 22 at addresses FFFF0h–FFFFFh in byte mode (or 7FFF8h–7FFFFh in word mode).

Customers may opt to have their code programmed by Spansion through the Spansion ExpressFlash

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.

8.2

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 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 group protect algorithm as shown in Figure 7.1 on page 20, substituting the sector group address

with the Secured Silicon Sector group address (A0=0, A1=1, A2=0, A3=1, A4=1, A5=0, A6=0, A7=0). This

allows in-system protection of the Secured Silicon Sector without raising any device pin to a high voltage.

Note that this method is only applicable to the Secured Silicon Sector.

 To verify the protect/unprotect status of the Secured Silicon Sector, follow the algorithm shown in

Figure 8.1 on page 24.

Once the Secured Silicon Sector is locked and verified, the system must write the Exit Secured Silicon Sector

Region command sequence to return to reading and writing the remainder of the array.

S29AS008J Datasheet(PDF) 23 Page - SPANSION

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