AM29DL32XG datasheet(21/58 Pages) AMD

21 / 58 page

February 9, 2005

Am29DL32xG

DA TA SH EET

It is possible to determine whether a sector is pro-

tected or unprotected. See the Autoselect Mode sec-

tion 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.

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 bottom-boot-configured device,

or the two sectors containing the highest addresses in

a top-boot-configured device.

If the system asserts VIH on the WP#/ACC pin, the de-

vice reverts to whether the two outermost 8K Byte

boot sectors were last set to be protected or unpro-

tected. That is, sector protection or unprotection for

these two sectors depends on whether they were last

protected or unprotected using the method described

in “Sector/Sector Block Protection and Unprotection”.

Note that the WP#/ACC pin must not be left floating or

unconnected; inconsistent behavior of the device may

result.

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 Tables

8 and 9).

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 V

ID (8.5 V – 12.5 V). During this mode, for-

merly protected sectors can be programmed or erased

by selecting the sector addresses. Once V

ID is re-

moved from the RESET# pin, all the previously pro-

tected sectors are protected again. Figure 1 shows the

algorithm, and Figure 24 shows the timing diagrams,

for this feature.

Figure 1.

Temporary Sector Unprotect Operation

START

Perform Erase or

Program Operations

RESET# = V

Temporary Sector

Unprotect Completed

(Note 2)

RESET# = V

(Note 1)

Notes:

1. All protected sectors unprotected (If WP#/ACC = V

IL,

outermost boot sectors will remain protected).

2. All previously protected sectors are protected once

again.

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