HY29F800 Datasheet, PDF (9/40 Pages) Hynix Semiconductor – 8 Megabit (1Mx8/512Kx16), 5 Volt-only, Flash Memory

The flow chart in Figure 1 illustrates the proce-
dure for protecting sectors, and timing specifica-
tions and waveforms are shown in the specifica-
tions section of this document. Verification of pro-
tection is accomplished as described in the Elec-
tronic ID Mode section and shown in the flow chart.
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
HY29F800
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.
Electronic ID Mode Operation
The Electronic ID mode provides manufacturer and
device identification and sector protection verifi-
cation through identifier codes output on DQ[7:0]
or DQ[15:0]. This mode is intended primarily for
programming equipment to automatically match
a device to be programmed with its correspond-
ing programming algorithm. The Electronic ID in-
formation can also be obtained by the host through
a command sequence, as described in the De-
vice Commands section.
Operation in the Electronic ID mode requires V_ID
on address pin A[9], with additional requirements
START
NOTE: All sectors must be
previously protected.
APPLY V _CC
Set: TRYCNT = 1
Set: NSEC = 0
Set: A9 = CE# = OE# = V _ID
Set: RESET# = V _IH
WE# = V _IL
Wait t_WPP2
WE# = V _IH
Set:
A9 = V _ID
OE# = CE# = V _IL
Set Sector Group Address:
A[18:12] = Sector NSEC
A0 = A6 = V _IL
A1 = V _IH
Read Data
NO
Data = 0x00?
Increment TRYCNT
NO
YES
TRYCNT = 1000?
YES
YES
NSEC = 18?
NO
NSEC = NSEC + 1
Remove V _ID from A9
SECTOR UNPROTECT
COMPLETE
DEVICE FAILURE
Figure 2. Sector Unprotect Procedure
Rev. 4.2/May 01
9