HY29F800
the duration of the RESET# pulse. The device also
resets the internal state machine to reading array
data. If an operation was interrupted by the as-
sertion of RESET#, it should be reinitiated once
the device is ready to accept another command
sequence to ensure data integrity.
Current is reduced for the duration of the RESET#
pulse as described in the Standby Operation sec-
tion above.
If RESET# is asserted during a program or erase
operation, the RY/BY# pin remains Low (busy) until
the internal reset operation is complete, which re-
quires a time of t
READY
(during Automatic Algo-
rithms). The system can thus monitor RY/BY# to
determine when the reset operation completes,
and can perform a read or write operation t
RB
after
RY/BY# goes High. If RESET# is asserted when
a program or erase operation is not executing (RY/
BY# pin is High), the reset operation is completed
within a time of t
RP
. In this case, the host can per-
form a read or write operation t
RH
after the RE-
SET# pin returns High .
The RESET# pin may be tied to the system reset
signal. Thus, a system reset would also reset the
device, enabling the system to read the boot-up
firmware from the Flash memory.
Sector Protect/Unprotect Operations
Hardware sector protection can be invoked to dis-
able program and erase operations in any single
sector or combination of sectors. This function is
typically used to protect data in the device from
unauthorized or accidental attempts to program
or erase the device while it is in the system (e.g.,
by a virus) and is implemented using program-
ming equipment. Sector unprotection re-enables
the program and erase operations in previously
protected sectors.
Table 1 identifies the nineteen sectors and the
address range that each covers. The device is
shipped with all sectors unprotected.
The sector protect/unprotect operations require a
high voltage (V
ID
) on address pin A[9] and the CE#
and/or OE# control pins, as detailed in Table 3.
When implementing these operations, note that
V
CC
must be applied to the device before applying
V
ID
, and that V
ID
should be removed before remov-
ing V
CC
from the device.
START
Wait t
W P P 1
A P P L Y V
CC
W E # = V
IH
A9 = V
ID
A[18:12] = Sector to Protect
OE# = CE# = A6 = A0 = V
IL
A1 = V
IH
Read Data
Set A9 = OE# = V
ID
NO
NO
Set TRYCNT = 1
Increment TRYCNT
Data = 0x01?
Set Address:
A[18:12] = Sector to Protect
CE# = V
IL
R E S E T # = V
IH
TRYCNT = 25?
YES
YES
R e m o v e V
ID
from A9
W E # = V
IL
Protect Another
Sector?
NO
SECTOR PROTECT
COMPLETE
DEVICE FAILURE
YES
Figure 1. Sector Protect Procedure
8
Rev. 4.0/Jan. 00
ETC [ ETC ]
