D A T A S H E E T
Unprotection”. Note: No external pullup is necessary
since the WP#/ACC pin has internal pullup to VCC
Write Protect (WP#)
.
The Write Protect function provides a hardware
method of protecting the first or last sector without
using VID. Write Protect is one of two functions pro-
vided by the WP#/ACC input.
Temporary Sector Group Unprotect
(Note: In this device, a sector group consists of four ad-
jacent sectors that are protected or unprotected at the
same time (see Table 4).
If the system asserts VIL on the WP#/ACC pin, the de-
vice disables program and erase functions in the first
or last sector independently of whether those sectors
were protected or unprotected using the method de-
scribed in “Sector Group Protection and Unprotection”.
Note that if WP#/ACC is at VIL when the device is in
the standby mode, the maximum input load current is
increased. See the table in “DC Characteristics”.
This feature allows temporary unprotection of previ-
ously protected sector groups to change data in-sys-
tem. The Sector Group Unprotect mode is activated by
setting the RESET# pin to VID. During this mode, for-
merly protected sector groups can be programmed or
erased by selecting the sector group addresses. Once
VID is removed from the RESET# pin, all the previously
protected sector groups are protected again. Figure 1
shows the algorithm, and Figure 23 shows the timing
diagrams, for this feature.
If the system asserts VIH on the WP#/ACC pin, the de-
vice reverts to whether the first or last sector was pre-
viously set to be protected or unprotected using the
method described in “Sector Group Protection and
START
RESET# = VID
(Note 1)
Perform Erase or
Program Operations
RESET# = VIH
Temporary Sector
Group Unprotect
Completed (Note 2)
Notes:
1. All protected sector groups unprotected (If WP# = VIL, the first or last sector will remain protected).
2. All previously protected sector groups are protected once again.
Figure 1. Temporary Sector Group Unprotect Operation
18
Am29LV640MH/L
December 14, 2005
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