HY29F400
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
V
ID
. While in this mode, formerly protected sec-
tors can be programmed or erased by invoking
the appropriate commands (see Device Com-
mands section). Once V
ID
is removed from RE-
SET#, all the previously protected sectors are pro-
tected again. Figure 3 illustrates the algorithm.
R E S E T # = V
IH
(All previously protected
sector groups return to
protected state)
START
R E S E T # = V
ID
(All protected sector groups
become unprotected)
Perform Program or Erase
Operations
TEMPORARY SECTOR
UNPROTECT COMPLETE
Figure 3. Temporary Sector Unprotect
START
NOTE: All sectors must be
previously protected.
Set Sector Address:
A[17:12] = Sector NSEC
A[0] = A[6] = V
IL
A[1] = V
IH
Increment TRYCNT
APPLY V
CC
Set: TRYCNT = 1
Read Data
NO
Set: NSEC = 0
Data = 0x00?
Set: A[9] = CE# = OE# = V
ID
NO
YES
TRYCNT = 1000?
Set: RESET# = V
IH
YES
YES
W E # = V
IL
NSEC = 10?
Wait t
W P P 2
Remove V
NO
NSEC = NSEC + 1
ID
from A[9]
W E # = V
IH
SECTOR UNPROTECT
COMPLETE
DEVICE FAILURE
Set:
A[9] = V
ID
OE# = CE# = V
IL
Figure 2. Sector Unprotect Procedure
Rev. 5.2/May 01
9
HYNIX [ HYNIX SEMICONDUCTOR ]
