L640DU21NF datasheet(20/57 Pages) AMD

20 / 57 page

Am29LV640D/Am29LV641D

22366C6 January 22, 2007

D A TA

SH EET

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 described

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 increased.

See the table in “DC Characteristics” on page 34.

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” on page 17.

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 on page 17)).

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, on page 18 shows the algo-

rithm, and Figure 21, on page 44 shows the timing dia-

grams, for this feature.

Figure 1.

Temporary Sector Group

Unprotect Operation

START

Perform Erase or

Program Operations

RESET# = VIH

Temporary Sector

Group Unprotect

Completed (Note 2)

RESET# = V

(Note 1)

Notes:

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

the first or last sector remains protected).

2. All previously protected sector groups are protected

once again.

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