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Write Protect / Accelerated Program (WP# / ACC)
The Write Protect function provides a hardware method to protect the first or last sector against erase
and program without using V
ID
.
When WP# is Low, the device protects the first or last sector regardless of whether these sectors were
previously protected or unprotected using the method described in “Sector Group Protection &
Unprotection”, Program and Erase operations in these sectors are ignored.
When WP# is High, the device reverts to the previous protection status of the first or last sector.
Program and Erase operations can now modify the data in those sectors unless the sector is protected
using Sector Group Protection.
Note that the WP# pin must not be left floating or unconnected.
When WP#/ACC is raised to V
HH
the memory automatically enters the Unlock Bypass mode(please
refer to “Command Definitions”), temporarily unprotects every protected sectors, and reduces the time
required for program operation. The system would use a two-cycle program command sequence as
required by the Unlock Bypass mode. When WP#/ACC returns to V
IH
or V
IL
, normal operation resumes.
The transitions from V
IH
or V
IL
to V
HH
and from V
HH
to V
IH
or V
IL
must be slower than t
B
VHH
B
, see Figure 5.
Note that the WP#/ACC pin must not be left floating or unconnected. In addition, WP#/ACC pin must
not be at V
HH
for operations other than accelerated programming. It could cause the device to be
damaged.
Never raise this pin to V
HH
from any mode except Read mode, otherwise the memory may be left in an
indeterminate state.
A 0.1μF capacitor should be connected between the WP#/ACC pin and the VSS Ground pin to
decouple the current surges from the power supply. The PCB track widths must be sufficient to carry
the currents required during Unlock Bypass Program.
Temporary Sector Group Unprotect
This feature allows temporary unprotection of previously protected
sector groups to change data while in-system. The Temporary
Sector Group Unprotect mode is activated by setting the RESET#
pin to V
B
ID
B
. During this mode, formerly protected sector groups can
be programmed or erased by simply selecting the sector group
addresses. Once V
B
ID
B
is removed from the RESET# pin, all the
previously protected sector groups are protected again. See
accompanying flowchart and timing diagrams in Figure 10 for more
details.
This Data Sheet may be revised by subsequent versions 2005 Eon Silicon Solution, Inc., www.essi.com.tw
or modifications due to changes in technical specifications.
Rev. C, Issue Date: 2007/01/23
EN29LV640
U
Start
Reset#=V
B
ID
B
B
(note 1)
B
Perform Erase or Program
Operations
RESET#=V
B
IH
B
Temporary Sector Group
Unprotect Completed
B
(note 2
)
Notes:
1. All protected sector groups are unprotected. (If
WP#/ACC=V
B
IL
protected.)
2. Previously protected sector groups are protected
again.
B
, the first or last sector will remain