AM29LV256MH103REF datasheet(28/69 Pages) AMD

28 / 69 page

Am29LV256M

December 16, 2005

D A TA SH EE T

Write Protect (WP#)

The Write Protect function provides a hardware

method of protecting the first or last sector without

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 independently of whether those sectors

were protected or unprotected using the method de-

scribed 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 Characteristics”.

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 addresses. Once V

ID is

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

tected 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# = 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.

AM29LV256MH103REF Datasheet(PDF) 28 Page - Advanced Micro Devices

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