HY29F400A Datasheet, PDF (8/40 Pages) Hynix Semiconductor – 4 Megabit (512Kx8/256Kx16) 5 Volt-only Flash Memory

HY29F400A
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 programming
equipment. Sector unprotection re-enables the
program and erase operations in previously pro-
tected sectors.
Table 1 identifies the eleven sectors and the ad-
dress range that each covers for both versions of
the device. 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.
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.
START
APPLY V_CC
Set TRYCNT = 1
Set A[9] = OE# = V_ID
Set Address:
A[17:12] = Sector to Protect
CE# = V_IL
RESET# = V_IH
WE# = V_IL
8
Wait t_WPP1
WE# = V_IH
A[9] = V_ID
A[17:12] = Sector to Protect
OE# = CE# = V_IL
A[6] = A[0] = V_IL, A[1] = V_IH
Read Data
NO
Data = 0x01?
Increment TRYCNT
NO
TRYCNT = 25?
YES
YES
Protect Another ^NO
Sector?
YES
DEVICE FAILURE
Figure 1. Sector Protect Procedure
Remove V_ID from A[9]
SECTOR PROTECT
COMPLETE
Rev. 1.0/Jan. 02