HY29F400A データシートの表示（PDF） - Hynix Semiconductor

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HY29F400A

4 Megabit (512Kx8/256Kx16) 5 Volt-only Flash Memory

Hynix Semiconductor 

The procedure for sector unprotection is illustrated

in the flow chart in Figure 2, and timing specifica-

tions and waveforms are given at the end of this

document. Note that to unprotect any sector, all

unprotected sectors must first be protected prior

to the first unprotect write cycle.

Sectors can also be temporarily unprotected as

described in the next section.

Temporary Sector Unprotect Operation

This feature allows temporary unprotection of pre-

viously protected sectors to allow changing the

data in-system. Temporary Sector Unprotect mode

is activated by setting the RESET# pin to VID. While

in this mode, formerly protected sectors can be

programmed or erased by invoking the appropri-

ate commands (see Device Commands section).

Once VID is removed from RESET#, all the previ-

ously protected sectors are protected again. Fig-

ure 3 illustrates the algorithm.

HY29F400A

START

RESET# = V ID

(All protected sector groups

become unprotected)

Perform Program or Erase

Operations

RESET# = V IH

(All previously protected

sector groups return to

protected state)

TEMPORARY SECTOR

UNPROTECT COMPLETE

Figure 3. Temporary Sector Unprotect

START

NOTE: All sectors must be

previously protected.

APPLY VCC

Set: TRYCNT = 1

Set: NSEC = 0

Set: A[9] = CE# = OE# = V ID

Set: RESET# = V IH

WE# = VIL

Wait tWPP2

WE# = VIH

Set:

A[9] = VID

OE# = CE# = V IL

Rev. 1.0/Jan. 02

Set Sector Address:

A[17:12] = Sector NSEC

A[0] = A[6] = V IL

A[1] = VIH

Read Data

NO

Data = 0x00?

Increment TRYCNT

NO

YES

TRYCNT = 1000?

YES

YES

NSEC = 10?

NO

NSEC = NSEC + 1

Remove VID from A[9]

SECTOR UNPROTECT

COMPLETE

DEVICE FAILURE

Figure 2. Sector Unprotect Procedure

9

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