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AM41PDS3224DB35IT Datasheet(PDF) 22 Page - Advanced Micro Devices |
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AM41PDS3224DB35IT Datasheet(HTML) 22 Page - Advanced Micro Devices |
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22 / 59 page  May 13, 2002 Am41PDS3224D 21 P R E L IMINARY SecSi (Secured Silicon) Sector Flash Memory Region The SecSi (Secured Silicon) Sector feature provides a Flash memory region that enables permanent part identification through an Electronic Serial Number (ESN). The SecSi Sector is 64 KBytes in length, and uses a SecSi Sector Indicator Bit (DQ7) to indicate whether or not the SecSi 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 secu- rity of the ESN once the product is shipped to the field. AMD offers the device with the SecSi Sector either fac tor y l o c k ed or c u s tomer lo c k abl e. The fac - tory-locked version is always protected when shipped from the factory, and has the SecSi (Secured Silicon) Sector Indicator Bit permanently set to a “1.” The cus- tomer-lockable version is shipped with the SecSi Sec- tor unprotected, allowing customers to utilize that sector in any manner they choose. The customer-lock- able version also has the SecSi Sector Indicator Bit permanently set to a “0.” Thus, the SecSi Sector Indi- cator Bit prevents customer-lockable devices from being used to replace devices that are factory locked. The system accesses the SecSi Sector through a command sequence (see “Enter SecSi Sector/Exit SecSi Sector Command Sequence”). After the system has written the Enter SecSi Sector command se- quence, it may read the SecSi Sector by using the ad- dresses normally occupied by the first sector (SA0). This mode of operation continues until the system is- sues the Exit SecSi 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 instead of the SecSi sector Factory Locked: SecSi Sector Programmed and Protected at the Factory In a factory locked device, the SecSi Sector is pro- tected when the device is shipped from the factory. The SecSi Sector cannot be modified in any way. The device is available preprogrammed 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 will have the 16-byte ESN in the lowest addressable memory area at addresses 000000h–000007h. In the Top Boot device the starting address of the ESN will be at the bottom of the lowest 8 Kbyte boot sector at addresses 1F8000h–1F8007h. Customers may opt to have their code programmed by AMD through the AMD ExpressFlash service. AMD programs the customer’s code, with or without the ran- dom ESN. The devices are then shipped from AMD’s factory with the permanently locked. Contact an AMD representative for details on using AMD’s Express- Flash service. Customer Lockable: SecSi Sector NOT Programmed or Protected at the Factory If the security feature is not required, the SecSi Sector can be treated as an additional Flash memory space, expanding the size of the available Flash array by 64 Kbytes. The SecSi Sector can be read, programmed, and erased as often as required. The SecSi Sector area can be protected using one of the following procedures: ■ Write the three-cycle Enter SecSi Sector Region command sequence, and then follow the in-system sector protect algorithm as shown in Figure 2, ex- cept that RESET# may be at either V IH or VID. This allows in-system protection of the SecSi Sector without raising any device pin to a high voltage. Note that this method is only applicable to the SecSi Sector. ■ Write the three-cycle Enter SecSi Sector Region command sequence, and then use the alternate method of sector protection described in the “Sec- tor/Sector Block Protection and Unprotection” sec- tion. Once the SecSi Sector is locked and verified, the sys- te m mus t wr i t e the E x i t Sec S i Sec tor Regi on command sequence to return to reading and writing the remainder of the array. The SecSi Sector protection must be used with cau- tion since, once protected, there is no procedure available for unprotecting the SecSi Sector area and none of the bits in the SecSi Sector memory space can be modified in any way. Hardware Data Protection The command sequence requirement of unlock cycles for programming or erasing provides data protection against inadvertent writes (refer to Table 10 for com- mand definitions). In addition, the following hardware data protection measures prevent accidental erasure or programming, which might otherwise be caused by spurious system level signals during V CC power-up and power-down transitions, or from system noise. Low V CC Write Inhibit When V CC is less than VLKO, the device does not ac- cept any write cycles. This protects data during V CC power-up and power-down. The command register and all internal program/erase circuits are disabled, and the device resets to reading array data. Subse- quent writes are ignored until V CC is greater than VLKO. |
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