AM29DL16XC datasheet(15/51 Pages) AMD

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Am29DL16xC

P R E L I M I NARY

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”. The two outermost 8

Kbyte boot sectors are the two sectors containing the

lowest addresses in a bottom-boot-configured device,

or the two sectors containing 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 8 Kbyte boot

sectors were last set to be protected or unprotected.

That is, sector protection or unprotection for these two

sectors depends on whether they were last protected

or unprotected using the method described in “Sec-

tor/Sector Block Protection and Unprotection”.

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

unconnected; inconsistent behavior of the device may

result.

Temporary Sector/Sector Block Unprotect

(Note: For the following discussion, the term “sector”

applies to both sectors and sector blocks. A sector

block consists of two or more adjacent sectors that are

protected or unprotected at the same time (see Tables

8 and 9).

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 V

ID (8.5 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 shows the

algorithm, and Figure 24 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)

21533C-6

Notes:

1. All protected sectors unprotected (If WP#/ACC = V

IL,

outermost boot sectors will remain protected).

2. All previously protected sectors are protected once

again.

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