AM29F400BT-150SCB datasheet(10/37 Pages) AMD

10 / 37 page

Am29F400B

PREL I M I N AR Y

Table 4.

Am29F400B Autoselect Codes (High Voltage Method)

L = Logic Low = VIL, H = Logic High = VIH, SA = Sector Address, X = Don’t care.

Sector Protection/Unprotection

The hardware sector protection feature disables both pro-

gram and erase operations in any sector. The hardware

sector unprotection feature re-enables both program and

erase operations in previously protected sectors.

Sector protection/unprotection must be implemented

using programming equipment. The procedure re-

quires a high voltage (VID) on address pin A9 and OE#.

Details on this method are provided in a supplement,

publication number 20185. Contact an AMD represent-

ative to obtain a copy of this document.

The device is shipped with all sectors unprotected.

AMD offers the option of programming and protecting

sectors at its factory prior to shipping the device

through AMD’s ExpressFlash™ Service. Contact an

AMD representative for details.

It is possible to determine whether a sector is protected

or unprotected. See “Autoselect Mode” for details.

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. Once VID is removed from the RE-

SET# pin, all the previously protected sectors are

protected again. Figure 1 shows the algorithm, and

Figure 18 shows the timing diagrams, for this feature.

Figure 1.

Temporary Sector Unprotect Operation

Hardware Data Protection

The command sequence requirement of unlock cycles

for programming or erasing provides data protection

against inadvertent writes (refer to Table 5 for com-

mand definitions). In addition, the following hardware

data protection measures prevent accidental erasure

or programming, which might otherwise be caused by

Description

Mode

CE#

OE#

WE#

A17

A12

A11

A10

DQ8

DQ15

DQ7

DQ0

Manufacturer ID: AMD

VID

XLX

01h

Device ID:

Am29F400B

(Top Boot Block)

Word

VID

XLX

22h

23h

Byte

23h

Device ID:

Am29F400B

(Bottom Boot Block)

Word

VID

XLX

22h

ABh

Byte

ABh

Sector Protection Verification

VID

XLX

01h

(protected)

00h

(unprotected)

START

Perform Erase or

Program Operations

RESET# = VIH

Temporary Sector

Unprotect Completed

(Note 2)

RESET# = VID

(Note 1)

Notes:

1. All protected sectors unprotected.

2. All previously protected sectors are protected once

again.

21505C-5

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