AM29DL400B datasheet(14/47 Pages) AMD

14 / 47 page

Am29DL400B

Table 4. Am29DL400B Autoselect Codes (High Voltage Method)

Note: L = Logic Low = VIL, H = Logic High = VIH, BA = Bank

Address, SA = Sector Address, X = Don’t care.

Sector Protection/Unprotection

The hardware sector protection feature disables both

program 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

can be implemented via two methods.

The primary method requires VID on the RESET# pin

only, and can be implemented either in-system or via

programming equipment. Figure 2 shows the algo-

rithms and Figure 24 shows the timing diagram. This

method uses standard microprocessor bus cycle tim-

ing. For sector unprotect, all unprotected sectors

must first be protected prior to the first sector un-

protect write cycle.

The alternate method intended only for program-

ming equipment requires VID on address pin A9 and

OE#. This method is compatible with programmer

routines written for earlier 3.0 volt-only AMD flash

devices. Publication number 22145 contains further

details; contact an AMD representative to request a

copy.

The device is shipped with all sectors unprotected.

AMD offers the option of programming and protect-

ing 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 pro-

tected or unprotected. See the Autoselect Mode

section 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 RESET# pin to VID (11.5 V – 12.5 V). During this

mode, formerly protected sectors can be pro-

gra mmed or era sed by selecting the se ctor

addresses. Once VID is removed from the RESET#

pin, all the previously protected sectors are

protected again. Figure 1 shows the algorithm, and

Figure 23 shows the timing diagrams, for this

feature.

Figure 1. Temporary Sector Unprotect

Operation

Description

Mode

CE#

OE# WE#

A17

A12

A11

A10

DQ8

DQ15

DQ7

DQ0

Manufacturer ID: AMD

VID

XLXL

01h

Device ID:

Am29DL400B

(Top Boot Block)

Word

VID

XLXL

22h

Byte

Device ID:

Am29DL400B

(Bottom Boot Block)

Word

VID

XLXL

22h

Byte

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.

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