AM29LV128ML123REF datasheet(22/66 Pages) AMD

22 / 66 page

Am29LV128MH/L

25270C7 January 31, 2007

D A TA

SH EE T

Write Protect (WP#)

The Write Protect function provides a hardware

method of protecting the first or last sector group with-

out using V

ID. Write Protect is one of two functions pro-

vided by the WP#/ACC input.

If the system asserts V

IL on the WP#/ACC pin, the de-

vice disables program and erase functions in the first

or last sector group independently of whether those

sector groups were protected or unprotected using the

method described in “Sector Group Protection and

Unprotection”. Note that if WP#/ACC is at V

IL when the

device is in the standby mode, the maximum input

load current is increased. See the table in “DC Char-

acteristics” on page 45

If the system asserts V

IH on the WP#/ACC pin, the de-

vice reverts to whether the first or last sector was pre-

viously set to be protected or unprotected using the

method described in “Sector Group Protection and

Unprotection”. Note that WP# has an internal pullup;

when unconnected, WP# is at V

IH.

Temporary Sector Group Unprotect

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. During this mode, for-

merly protected sector groups can be programmed or

erased by selecting the sector group addresses. Once

ID is removed from the RESET# pin, all the previously

protected sector groups are protected again. Figure 1

shows the algorithm, and Figure 24 shows the timing

diagrams, 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 will remain protected).

2. All previously protected sector groups are protected

once again.

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