MX29LV320AT/B
It is also possible to determine if the chip is unprotected
in the system by writing the Read Silicon ID command.
Performing a read operation with A1=VIH, it will produce
00H at data outputs(Q0-Q7) for an unprotected sector.It
is noted that all sectors are unprotected after the chip
unprotect algorithm is completed.
AUTOMATIC SELECT OPERATION
Flash memories are intended for use in applications where
the local CPU alters memory contents. As such, manu-
facturer and device codes must be accessible while the
device resides in the target system. PROM program-
mers typically access signature codes by raising A9 to
a high voltage. However, multiplexing high voltage onto
address lines is not generally desired system design prac-
tice.
TEMPORARY SECTOR GROUP UNPROTECT
OPERATION
MX29LV320AT/B provides hardware method to access
the Automatic Select operation.This method requiresVID
on A9 pin, VIL on CE, OE, A6, and A1 pins.When apply-
ing VIL on A0 pin, the device will output MXIC's manu-
facture code of C2H. When applying VIH on A0 pin, the
device will output MX29LV320AT/B device code of 22A7h
and 22A8h.
This feature allows temporary unprotection of previously
protected sector to change data in-system.The Tempo-
rary Sector Unprotect mode is activated by setting the
RESET pin to VID(11.5V-12.5V). During this mode, for-
merly protected sectors can be programmed or erased
as un-protected sector. Once VID is remove from the
RESET pin, all the previously protected sectors are pro-
tected again.
VERIFY SECTOR GROUP PROTECT STATUS
OPERATION
WRITE PROTECT (WP)
MX29LV320AT/B provides hardware method for sector
group protect status verify. This method requires VID on
A9 pin, VIH on WE and A1 pins, VIL on CE, OE, A6, and
A0 pins, and sector address on A12 to A20 pins. When
the identified sector is protected, the device will output
01H.When the identified sector is not protect, the device
will output 00H.
The write protect function provides a hardware method
to protect boot sectors without using VID.
If the system asserts VIL on the WP/ACC pin, the de-
vice disables program and erase functions in the two
"outermost" 8 Kbyte boot sectors independently of
whether those sectors were protected or unprotected
using the method described in Sector/Sector Group Pro-
tection and Chip Unprotection". The two outermost 8
Kbyte boot sectors are the two sectors containing the
lowest addresses in a bottom-boot-configured device, or
the two sectors containing the highest addresses in a
top-boot-configured device.
SECURITY SECTOR FLASH MEMORY REGION
The Security Sector (Security Sector) feature provides a
Flash memory region that enables permanent part iden-
tification through an Electronic Serial Number (ESN).The
Security Sector is 64 Kbytes (32 Kwords) in length, and
uses a Security Sector Indicator Bit (Q7) to indicate
whether or not the Security Sector is locked when shipped
from the factory. This bit is per-manently set at the fac-
tory and cannot be changed, which prevents cloning of a
factory locked part.This ensures the security of the ESN
once the product is shipped to the field.
If the system asserts VIH on the WP/ACC pin, the de-
vice reverts to whether the two outermost 8K Byte boot
sectors were last set to be protected or unprotected.That
is, sector protection or unprotection for these two sec-
tors depends on whether they were last protected or un-
protected using the method described in "Sector/Sector
Group Protection and Chip Unprotection".
MXIC offers the device with the Security Sector either
factory locked or customer lockable. The factory-locked
version is always protected when shipped from the fac-
tory, and has the Security on Silicon Sector (Security
Sector) Indicator Bit permanently set to a "1". The cus-
tomer-lockable version is shipped with the unprotected,
allowing customers to utilize the that sector in any man-
Note that the WP/ACC pin must not be left floating or
unconnected; inconsistent behavior of the device may
result.
P/N:PM1008
REV. 1.1, MAY 28, 2004
13
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