S29AS008J datasheet(19/56 Pages) CYPRESS

19 / 56 page

Document Number: 002-00870 Rev.*K

Page 19 of 56

S29AS008J

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 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 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 16, 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 20.

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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