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AM41DL1624DT70IT Datasheet(PDF) 23 Page - Advanced Micro Devices |
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AM41DL1624DT70IT Datasheet(HTML) 23 Page - Advanced Micro Devices |
23 / 63 page 22 Am41DL16x4D 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 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 security of the ESN once the product is shipped to the field. Current version of this device has 64 Kbytes; future ver- sions will have only 256 bytes. This should be considered during system design. 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 Sector Indicator Bit permanently set to a “1.” The customer-lockable version is shipped with the unprotected, allowing cus- tomers to utilize the that sector in any manner they choose. The customer-lockable version has the SecSi Sector Indicator Bit permanently set to a “0.” Thus, the SecSi Sector Indicator 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 addresses normally occupied by the boot sectors. This mode of operation continues until the system issues 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 send- ing commands to the boot sectors. 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 a random, se- cure ESN only In devices that have an ESN, the Top Boot device will have the 16-byte ESN, with the starting address of the ESN will be at the bottom of the lowest 8 Kbyte boot sector at addresses F8000h–F8007h in word mode (or 1F0000h–1F000Fh in byte mode). 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. Current version of this device has 64 Kbytes; future versions will have only 256 bytes. This should be considered during system design. The SecSi Sector can be read, programmed, and erased as often as required. Note that the accelerated program- ming (ACC) and unlock bypass functions are not available when programming the SecSi Sector. The SecSi Sector area can be protected using one of the following procedures: s 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 without raising any device pin to a high voltage. Note that this method is only applicable to the SecSi Sector. s Write the three-cycle Enter SecSi Sector Region command sequence, and then use the alternate method of sector protection described in the “The autoselect mode provides manufacturer and device identification, and sector protection verification, through identifier codes output on DQ7–DQ0. The autoselect codes can be accessed in-system through the com- mand register. Refer to the Autoselect Command Se- quence section for more information.Sector/Sector Block Protection and Unprotection”. 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 16 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 |
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