L640GU53RI datasheet(20/55 Pages) AMD

20 / 55 page

Am29LV641G

June 14, 2005

ADV ANCE

I N FO RMAT I O N

Write Protect (WP#)

The Write Protect function provides a hardware

method of protecting the first or last sector without

using V

ID.

If the system asserts V

IL on the WP# pin, the device

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# is at V

IL when the device is in the

standby mode, the maximum input load current is in-

creased. See the table in “DC Characteristics”.

If the system asserts V

IH on the WP# pin, the device

reverts to whether the first or last sector was previ-

ously set to be protected or unprotected using the

method described in “Sector Group Protection and

Unprotection”.

Temporary Sector Group Unprotect

(Note: In this device, a sector group consists of four adjacent

sectors that are protected or unprotected at the same time

(see Table 4)).

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 V

ID (8.5 V – 12.5 V). During

this mode, formerly protected sector groups can be

programmed or erased by selecting the sector group

addresses. Once V

ID is removed from the RESET#

pin, all the previously protected sector groups are

protected again. Figure 1 shows the algorithm, and

Figure 22 shows the timing diagrams, for this feature.

Figure 1.

Temporary Sector Group

Unprotect Operation

START

Perform Erase or

Program Operations

RESET# = V

Temporary Sector

Group Unprotect

Completed (Note 2)

RESET# = V

(Note 1)

Notes:

1. All protected sector groups unprotected (If WP# = V

IL,

the first or last sector will remain protected).

2. All previously protected sector groups are protected

once again.

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