A29400 Series
Sector Protection/Unprotection
Temporary Sector Unprotect
The hardware sector protection feature disables both
program and erase operations in any sector. The hardware
sector unprotection feature re-enables both program and
erase operations in previously protected sectors.
This feature allows temporary unprotection of previous
protected sectors to change data in-system. The Sector
Unprotect mode is activated by setting the
pin to
RESET
VID. During this mode, formerly protected sectors can be
Sector protection/unprotection must be implemented using
programming equipment. The procedure requires a high
voltage (VID) on address pin A9 and the control pins.
The device is shipped with all sectors unprotected.
It is possible to determine whether a sector is protected or
unprotected. See "Autoselect Mode" for details.
programmed or erased by selecting the sector addresses.
Once VID is removed from the
pin, all the previously
RESET
protected sectors are protected again. Figure 1 shows the
algorithm, and the Temporary Sector Unprotect diagram
shows the timing waveforms, for this feature.
Hardware Data Protection
START
The requirement of command unlocking sequence for
programming or erasing provides data protection against
inadvertent writes (refer to the Command Definitions table).
In addition, the following hardware data protection measures
prevent accidental erasure or programming, which might
otherwise be caused by spurious system level signals during
VCC power-up transitions, or from system noise. The device
is powered up to read array data to avoid accidentally writing
data to the array.
RESET = VID
(Note 1)
Perform Erase or
Program Operations
Write Pulse "Glitch" Protection
Noise pulses of less than 5ns (typical) on
do not initiate a write cycle.
,
or
WE
OE CE
Logical Inhibit
Write cycles are inhibited by holding any one of
RESET = VIH
=VIL,
OE
CE
= VIH or
= VIH. To initiate a write cycle,
and
WE
CE
must be a logical zero while
is a logical one.
WE
OE
Temporary Sector
Unprotect
Completed (Note 2)
Power-Up Write Inhibit
If
=
= VIL and
= VIH during power up, the
OE
WE
device does not accept commands on the rising edge of
. The internal state machine is automatically reset to
CE
WE
reading array data on the initial power-up.
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once again.
Figure 1. Temporary Sector Unprotect Operation
PRELIMINARY
(February, 2001, Version 0.1)
8
AMIC Technology, Inc.
AMICC [ AMIC TECHNOLOGY ]
