AM29F160D datasheet(14/46 Pages) AMD

14 / 46 page

Am29F160D

Write Protect (WP#)

The Write Protect function provides a hardware

method of protecting the 16 Kbyte boot sector without

using VID.

If the system asserts VIL on the WP# pin, the device

disables program and erase functions for the 16 Kbyte

boot sector (SA34 for top boot device and SA0 for bot-

tom boot device) independently of whether those sec-

tors were protected or unprotected using the method

described in “Sector Protection/Unprotection”.

If the system asserts VIH on the WP# pin, the device

reverts to whether the 16 Kbyte boot sector was previ-

ously set to be protected or unprotected using the

method described in “Sector Protection/Unprotection”.

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. During this mode, formerly protected

sectors can be programmed or erased by selecting the

sector addresses. Note, however, that the boot sector

will still be protected if WP# is asserted low. Once VID

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

tected sectors are protected again. Figure shows the

algorithm, and Figure 19 shows the timing diagrams,

for this feature.

Figure 1.

Temporary Sector Unprotect Operation

START

Perform Erase or

Program Operations

RESET# = VIH

Temporary Sector

Unprotect Completed

(Note 2)

RESET# = VID

(Note 1)

Notes:

1. All protected sectors unprotected. Boot sector remains

protected if WP# is low.

2. All previously protected sectors are protected once

again.

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