P R E L I M I N A R Y
Sector protection and unprotection can be imple-
mented as follows.
Temporary Sector/Sector Block 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
10).
Sector protection and unprotection requires VID on the
RESET# pin only, and can be implemented either
in-system or via programming equipment. Figure 2
shows the algorithms and Figure 26 shows the timing
diagram. This method uses standard microprocessor
bus cycle timing. For sector unprotect, all unprotected
sectors must first be protected prior to the first sector
unprotect write cycle.
This feature allows temporary unprotection of previ-
ously protected sectors to change data in-system. The
Sector Unprotect mode is activated by setting the RE-
SET# pin to VID (11.5 V – 12.5 V). 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 pro-
tected sectors are protected again. Figure 1 shows the
algorithm, and Figure 25 shows the timing diagrams,
for this feature.
The device is shipped with all sectors unprotected.
It is possible to determine whether a sector is pro-
tected or unprotected. See the Autoselect Mode
section for details.
Write Protect (WP#)
The Write Protect function provides a hardware
method of protecting certain boot sectors without
using VID. This function is one of two provided by the
WP#/ACC pin.
START
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 Block
Protection and Unprotection”. The two outermost 8
Kbyte boot sectors are the two sectors containing the
lowest addresses in a top-boot-configured device, or
the two sectors containing the highest addresses in a
top-boot-configured device.
RESET# = VID
(Note 1)
Perform Erase or
Program Operations
RESET# = VIH
If the system asserts VIH on the WP#/ACC pin, the de-
vice reverts to whether the two outermost 8 Kbyte boot
sectors were last set to be protected or unprotected.
That is, sector protection or unprotection for these two
sectors depends on whether they were last protected
or unprotected using the method described in “Sec-
tor/Sector Block Protection and Unprotection”.
Temporary Sector
Unprotect Completed
(Note 2)
Notes:
Note that the WP#/ACC pin must not be left floating or
unconnected; inconsistent behavior of the device may
result.
1. All protected sectors unprotected (If WP#/ACC = VIL,
outermost boot sectors will remain protected).
2. All previously protected sectors are protected once
again.
Figure 1. Temporary Sector Unprotect Operation
22
Am41DL32x8G
September 5, 2002
AMD [ AMD ]
