cept that
RESET# may be at either V
IH
or V
ID
. This allows in-system protec-
tion of the SecSi Sector without raising any device pin to a high voltage. Note
that this method is only applicable to the SecSi Sector.
To verify the protect/unprotect status of the SecSi Sector, follow the algo-
rithm shown in Figure 3.
Once the SecSi Sector is programmed, locked and verified, the system must
write the Exit SecSi Sector Region command sequence to return to reading and
writing within the remainder of the array.
Factory Locked: SecSi Sector Programmed and Protected At the
Factory
In devices with an ESN, the SecSi Sector is protected when the device is shipped
from the factory. The SecSi Sector cannot be modified in any way. An ESN Fac-
tory Locked device has a 16-byte random ESN at addresses 0F8000h–0F8007h.
Please contact your local sales office or representative for details on ordering ESN
Factory Locked devices.
Customers may opt to have their code programmed by the manufacturer
through the ExpressFlash service (Express Flash Factory Locked). The devices
are then shipped from the factory with the SecSi Sector permanently locked.
Contact an sales office or representative for details on using the ExpressFlash
service.
START
RESET# =
V
IH
or V
ID
Wait 1 ms
Write 60h to
any address
If data = 00h,
SecSi Sector is
unprotected.
If data = 01h,
SecSi Sector is
protected.
Remove V
IH
or V
ID
from RESET#
Write reset
command
SecSi Sector
Protect Verify
complete
Write 40h to SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
Read from SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
Figure 3.
SecSi Sector Protect Verify
Common Flash Memory Interface (CFI)
The Common Flash Interface (CFI) specification outlines device and host system
software interrogation handshake, which allows specific vendor-specified soft-
ware algorithms to be used for entire families of devices. Software support can
then be device-independent, JEDEC ID-independent, and forward- and back-
April 21, 2004 S29AL016M_00A4
S29AL016M
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