
April 30, 2004 S29GLxxxM_00A5
S29GLxxxM MirrorBit
TM
 Flash Family
97
P r e l i m i n a r y
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 1
.
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 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 
Spansion programming service (Customer Factory Locked). The devices are then 
shipped from the factory with the SecSi Sector permanently locked. Contact your 
sales representative for details on using the Spansion programming service.
Write Protect (WP#)
The Write Protect function provides a hardware method of protecting the first or 
last sector group 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 group independently of whether those 
sector groups 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 in-
creased. See the table in “DC Characteristics” section on page 122. 
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 un-
protected using the method described in “Sector Group Protection and 
Unprotection”. 
Note that WP# has an internal pullup; when uncon-
nected, WP# is at V
IH
.
Hardware Data Protection
The command sequence requirement of unlock cycles for programming or erasing 
provides data protection against inadvertent writes (refer to Tables 
16
 and 
17
 for 
command definitions). In addition, the following hardware data protection mea-
sures 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 V
LKO
, the device does not accept any write cycles. This pro-
tects 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
.