L320DB12VC datasheet(20/57 Pages) AMD

20 / 57 page

Am29LV320D

December 14, 2005

DA TA SH EET

Write Protect (WP#)

The Write Protect function provides a hardware

method of protecting certain boot sectors without

using V

ID. This function is one of two provided by the

WP#/ACC pin.

If the system asserts V

IL 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” on page 17. The two out-

ermost 8 Kbyte boot sectors are the two sectors con-

taining

the

lo w e st

addre sses

bottom-boot-configured device, or the two sectors con-

taining the highest addresses in a top-boot-configured

device.

If the system asserts V

IH 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”

on page 17.

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

unconnected; inconsistent behavior of the device may

result.

Temporary Sector Unprotect

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 VID (11.5 V – 12.5 V). During this mode,

formerly protected sectors can be programmed or

erased by selecting the sector addresses. Once V

ID is

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

tected sectors are protected again. Figure 1, on page

18 shows the algorithm, and Figure 23, on page 46

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 remain protected).

2. All previously protected sectors are protected once

again.

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