D A T A S H E E T
Sector protection/unprotection must be implemented
using programming equipment. The procedure
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadvertent writes (refer to the Command Defi-
nitions table). In addition, the following hardware data
protection measures prevent accidental erasure or pro-
gramming, which might otherwise be caused by
requires a high voltage (V ) on address pin A9 and the
ID
control pins. Details on this method are provided in the
supplements, publication numbers 20819
(Am29F002B) and 21183 (Am29F002NB). Contact an
AMD representative to obtain a copy of the appropriate
document.
spurious system level signals during V power-up and
CC
The device is shipped with all sectors unprotected.
AMD offers the option of programming and protecting
sectors at its factory prior to shipping the device
through AMD’s ExpressFlash™ Service. Contact an
AMD representative for details.
power-down transitions, or from system noise.
Low V
Write Inhibit
CC
When V
is less than V
, the device does not
LKO
CC
accept any write cycles. This protects data during V
power-up and power-down. The command register and
all internal program/erase circuits are disabled, and the
CC
It is possible to determine whether a sector is protected
or unprotected. See “Autoselect Mode” for details.
device resets. Subsequent writes are ignored until V
CC
is greater than V
proper signals to the control pins to prevent uninten-
. The system must provide the
LKO
Temporary Sector Unprotect
Note: This feature requires the RESET# pin and is
tional writes when V is greater than V
.
CC
LKO
therefore not available on the Am29F002NB.
Write Pulse “Glitch” Protection
This feature allows temporary unprotection of previ-
ously protected sectors to change data in-system. The
Sector Unprotect mode is activated by setting the
Noise pulses of less than 5 ns (typical) on OE#, CE# or
WE# do not initiate a write cycle.
Logical Inhibit
RESET# pin to V . During this mode, formerly pro-
ID
tected sectors can be programmed or erased by
Write cycles are inhibited by holding any one of OE# =
V , CE# = V or WE# = V . To initiate a write cycle,
selecting the sector addresses. Once V is removed
ID
IL
IH
IH
from the RESET# pin, all the previously protected
sectors are protected again. Figure 1 shows the algo-
rithm, and the Temporary Sector Unprotect diagram
shows the timing waveforms, for this feature.
CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = V and OE# = V during power up, the
IL
IH
device does not accept commands on the rising edge
of WE#. The internal state machine is automatically
reset to reading array data on power-up.
START
RESET# = VID
(Note 1)
Perform Erase or
Program Operations
RESET# = VIH
Temporary Sector
Unprotect
Completed (Note 2)
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once
again.
Figure 1. Temporary Sector Unprotect Operation
November 17, 2009 21527D8
Am29F002B/Am29F002NB
11
CYPRESS [ CYPRESS ]
