MX26L3220
sion has the secured sector Indicator Bit permanently
set to a "0". Therefore, the Secured Silicon Sector Indi-
cator Bit permanently set to a "0".Therefore, the Second
Silicon Sector Indicator Bit prevents customer, lockable
device from being used to replace devices that are fac-
tory locked.
FACTORY LOCKED:Secured Silicon Sector
Programmed and Protected At the Factory
In device 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.A factory locked device has an 8-word random ESN
at address 000000h-000007h.
The system access the Secured Silicon Sector through
a command sequence (refer to "Enter Secured Silicon/
Exit Secured Silicon Sector command Sequence). After
the system has written the Enter Secured Silicon Sector
command sequence, it may read the Secured Silicon
Sector by using the address normally occupied by the
address 000000h-0001FFh.This mode of operation con-
tinues until the system issues the Exit Secured Silicon
Sector command sequence, or until power is removed
from the device. On power-up, or following a hardware
reset, the device reverts to sending command to ad-
dress 000000h-0001FFFh.
CUSTOMER LOCKABLE:Secured Silicon
Sector NOT Programmed or Protected At the
Factory
As an alternative to the factory-locked version, the device
may be ordered such that the customer may program
and protect the 512-word Secured Silicon Sector.
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.
LOW VCC WRITE INHIBIT
When VCC is less than VLKO the device does not ac-
cept any write cycles. This protects dataduring VCC
power-up and power-down.The command register and
all internal program/erase circuits are disabled, and the
device resets. Subsequent writes are ignored until VCC
is greater thanVLKO. The system must provide the proper
signals to the control pins to prevent unintentional write
whenVCC is greater thanVLKO.
The Secured Silicon Sector area can be protected using
the following procedures:
Write the three-cycle Enter Secured Silicon Sector Region
command sequence. This allows in-system protection
of the Secured Silicon Sector without raising any device
pin to a high voltage. Note that method is only applicable
to the Secured Silicon Sector.
WRITE PULSE "GLITCH" PROTECTION
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 the remainder of the array.
Noise pulses of less than 5ns(typical) on CE or WE will
not initiate a write cycle.
LOGICAL INHIBIT
Writing is inhibited by holding any one of OE =VIL, CE =
VIH or WE = VIH. To initiate a write cycle CE and WE
must be a logical zero while OE is a logical one.
POWER-UP SEQUENCE
The MX26L3220 powers up in the Read only mode. In
addition, the memory contents may only be altered after
successful completion of the predefined command se-
quences.
P/N:PM0826
REV. 0.5, JAN. 29, 2002
9
Macronix [ MACRONIX INTERNATIONAL ]
