D at a
S hee t
8.18.1
Customer Lockable: Secured Silicon Sector NOT Programmed or Protected
At the Factory
Unless otherwise specified, the device is shipped such that the customer may program and protect the 256-
byte Secured Silicon sector.
The system may program the Secured Silicon Sector using the write-buffer, accelerated and/or unlock
bypass methods, in addition to the standard programming command sequence. See
Programming and protecting the Secured Silicon Sector 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.
The Secured Silicon Sector area can be protected using one of the following procedures:
Write the three-cycle Enter Secured Silicon Sector Region command.
To verify the protect/unprotect status of the Secured Silicon Sector, follow the algorithm.
Once the Secured Silicon Sector is programmed, locked and verified, the system must write the Exit Secured
Silicon Sector Region command sequence to return to reading and writing within the remainder of the array.
8.18.2
Factory Locked: Secured Silicon Sector Programmed and Protected At the
Factory
In devices with an ESN, the Secured Silicon Sector is protected when the device is shipped from the factory.
The Secured Silicon Sector cannot be modified in any way. An ESN Factory Locked device has an 16-byte
random ESN at addresses 000000h–000007h. Please contact your sales representative for details on
ordering ESN Factory Locked devices.
Customers may opt to have their code programmed by the factory through the ExpressFlash service (Express
Flash Factory Locked). The devices are then shipped from the factory with the Secured Silicon Sector
permanently locked. Contact your sales representative for details on using the ExpressFlash service.
8.19
Write Protect (WP/ACC#)
The Write Protect function provides a hardware method of protecting the first or last sector without using V
ID
.
Write Protect is one of two functions provided by the WP#/ACC input.
If the system asserts V
IL
on the WP#/ACC pin, the device disables program and erase functions in the first or
last sector independently of whether those sectors were protected or unprotected. Note that if WP#/ACC is at
V
IL
when the device is in the standby mode, the maximum input load current is increased. See the table in
If the system asserts V
IH
on the WP#/ACC pin, the device reverts to whether the first or last sector was
previously set to be protected or unprotected using the method described in
Note that WP/ACC# contains an internal pullup; when unconnected, WP/ACC# is at V
IH
.
8.20
Hardware Data Protection
The command sequence requirement of unlock cycles for programming or erasing provides data protection
against inadvertent writes (refer to
and
for command
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.
8.20.1
Low V
CC
Write Inhibit
When V
CC
is less than V
LKO
, the device does not accept 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 the read mode. Subsequent writes are ignored until V
CC
is greater than V
LKO
. The
system must provide the proper signals to the control pins to prevent unintentional writes when V
CC
is greater
than V
LKO
.
36
S29GL-N MirrorBit
®
Flash Family
S29GL-N_01_09 November 16, 2007
SPANSION [ SPANSION ]
