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 . Write Protect is one of two functions provided
ID
by the WP#/ACC input.
If the system asserts V on the WP#/ACC pin, the device disables program and
IL
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
on the WP#/ACC pin, the device reverts to
IH
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
transitions, or from system noise.
power-up and power-down
CC
Low V
Write Inhibit
CC
When V is less than V
, the device does not accept any write cycles. This pro-
LKO
CC
tects data during V power-up and power-down. The command register and all
CC
internal program/erase circuits are disabled, and the device resets to the read
mode. Subsequent writes are ignored until V is greater than V
. The system
LKO
CC
must provide the proper signals to the control pins to prevent unintentional writes
when V is greater than V
.
LKO
CC
April 30, 2004 S29GLxxxM_00A5
S29GLxxxM MirrorBitTM Flash Family
97
SPANSION [ SPANSION ]
