If the system asserts VIH on the WP#/ACC pin, the de-
vice reverts to whether sectors 0, 1, 140, and 141
were last set to be protected or unprotected. That is,
sector protection or unprotection for these sectors de-
pends on whether they were last protected or unpro-
tected using the method described in “Sector/Sector
Block Protection and Unprotection”.
Temporary Sector Unprotect
(Note: For the following discussion, the term “sector”
applies to both sectors and sector blocks. A sector
block consists of two or more adjacent sectors that are
protected or unprotected at the same time (see Table
6).
This feature allows temporary unprotection of previ-
ously protected sectors to change data in-system. The
Temporary Sector Unprotect mode is activated by set-
ting the RESET# pin to VID. During this mode, formerly
protected sectors can be programmed or erased by
selecting the sector addresses. Once VID is removed
from the RESET# pin, all the previously protected sec-
tors are protected again. Figure 1 shows the algo-
rithm, and Figure 25 shows the timing diagrams, for
this feature. If the WP#/ACC pin is at VIL, sectors 0, 1,
140, and 141 will remain protected during the Tempo-
rary sector Unprotect mode.
Note that the WP#/ACC pin must not be left floating or
unconnected; inconsistent behavior of the device may
result.
Table 7. WP#/ACC Modes
Device
Mode
WP# Input
Voltage
Disables programming and erasing in
SA0, SA1, SA140, and SA141
VIL
Enables programming and erasing in
SA0, SA1, SA140, and SA141,
dependent on whether they were last
protected or unprotected.
VIH
Enables accelerated programming
(ACC). See “Accelerated Program
Operation” on page 9.
VHH
START
RESET# = VID
(Note 1)
Perform Erase or
Program Operations
RESET# = VIH
Temporary Sector
Unprotect Completed
(Note 2)
Notes:
1. All protected sectors unprotected (If WP#/ACC = VIL,
sectors 0, 1, 140, and 141 will remain protected).
2. All previously protected sectors are protected once
again.
Figure 1. Temporary Sector Unprotect Operation
16
Am29DL640H
June 7, 2005
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