S29AS016J datasheet(21/59 Pages) CYPRESS

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Document Number: 002-01122 Rev.*L

Page 21 of 59

S29AS016J

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.

Cypress 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 28). 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 38 at addresses 1FFFF0–1FFFFF in byte

mode (or FFFF8–FFFFF in word mode).

Customers may opt to have their code programmed by Cypress through the Cypress ExpressFlash service. Cypress programs the

customer’s code, with or without the random ESN. The devices are then shipped from the Cypress factory with the Secured Silicon

Sector permanently locked. Contact a Cypress representative for details on using the Cypress 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 Cypress. Note that the unlock bypass function is 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 18, 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 22.

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.

The Secured Silicon Sector protection must be used with caution since, once protected, there is no procedure available for

unprotecting the Secured Silicon Sector area, and none of the bits in the Secured Silicon Sector memory space can be modified in

any way.

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