AM29DL640D AMD, AM29DL640D Datasheet - Page 19

• Manufacturer Part Number: AM29DL640D
• Description: 64 Megabit CMOS 3.0 Volt-only / Simultaneous Read/Write Flash Memory
• Manufacturer: AMD

SecSi™ (Secured Silicon) Sector Secure
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 Secure is 256 bytes in
length, and uses a SecSi Sector Secure Indicator Bit
(DQ7) to indicate whether or not the SecSi Sector Se-
cure 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.
AMD offers the device with the SecSi Sector either
factor y locked o r custom er locka ble . Th e 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 Secure unprotected, allowing customers to utilize
the that sector in any manner they choose. The cus-
tomer-lockable version has the SecSi (Secured Sili-
con) Sector Indicator Bit permanently set to a “0.”
Thus, the SecSi Sector Secure Indicator Bit prevents
customer-lockable devices from being used to replace
devices that are factory locked.
The system accesses the SecSi Sector Secure
through a command sequence (see “Enter SecSi™
Sector Secure/Exit SecSi Sector Secure Command
Sequence”). After the system has written the Enter
SecSi Sector Secure command sequence, it may read
the SecSi Sector Secure by using the addresses nor-
mally occupied by the boot sectors. This mode of op-
eration continues until the system issues the Exit
SecSi Sector command sequence, or until power is re-
moved from the device. On power-up, or following a
hardware reset, the device reverts to sending com-
mands to the first 256 bytes of Sector 0.
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 preprogrammed with both a random number
and a secure ESN. The 8-word random number will in
the lowest addressable memory area at addresses
0 0 0 0 0 0 h – 0 0 0 0 0 7 h
000000h–00000Fh in byte mode). The secure ESN
will be programmed in the next 8 words at addresses
000008h–00000Fh. The device is available prepro-
grammed with one of the following:
A random, secure ESN only
i n
w o r d
A D V A N C E
m o d e
Am29DL640D
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I N F O R M A T I O N
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 word
mode (or 000000h–00000Fh in byte mode). In the Top
Boot device the starting address of the ESN will be at
the bottom of the lowest 8 Kbyte boot sector at ad-
dresses 1F8000h–1F8007h in word mode (or ad-
dresses 3F0000h–3F000Fh in byte mode).
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 SecSi Sector permanently locked.
Contact an AMD representative for details on using
AMD’s ExpressFlash service.
Customer Lockable: SecSi Sector Secure 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, pro-
grammed, and erased as often as required. Note that
the accelerated programming (ACC) and unlock by-
pass functions are not available when programming
the SecSi Sector.
The SecSi Sector area can be protected using one of
the following procedures:
Once the SecSi Sector Secure is locked and verified,
the system must write the Exit SecSi Sector Secure
Region command sequence to return to reading and
writing the remainder of the array.
The SecSi Sector lock must be used with caution
since, once locked, there is no procedure available for
unlocking the SecSi Sector area and none of the bits
in the SecSi Sector Secure memory space can be
modified in any way.
Customer code through the ExpressFlash service
Both a random, secure ESN and customer code
through the ExpressFlash service.
Write the three-cycle Enter SecSi Sector Secure
Region command sequence, and then follow the
in-system sector protect algorithm as shown in Fig-
ure 2, except that RESET# may be at either V
V
Sector Secure Region without raising any device
pin to a high voltage. Note that this method is only
applicable to the SecSi Sector Secure.
Write the three-cycle Enter SecSi Sector Secure
Region command sequence, and then use the alter-
nate method of sector protection described in the
“Sector/Sector Block Protection and Unprotection”
section.
ID
. This allows in-system protection of the SecSi
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