AS29CF160T-55TIN
AS29CF160B-55TIN
Sector Protection/Unprotection
Write Pulse "Glitch" Protection
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.
It is possible to determine whether a sector is protected or
unprotected. See “Autoselect Mode” for details.
Noise pulses of less than 5ns (typical) on
do not initiate a write cycle.
,
or
OE CE
WE
Logical Inhibit
Write cycles are inhibited by holding any one of
=VIL,
OE
CE
= VIH or
= VIH. To initiate a write cycle,
and
WE
CE
Sector protection / unprotection can be implemented via two
must be a logical zero while
is a logical one.
WE
OE
methods. The primary method requires VID on the
pin
RESET
only, and can be implemented either in-system or via
programming equipment. Figure 2 shows the algorithm and
the Sector Protect / Unprotect Timing Diagram illustrates the
timing waveforms for this feature. This method uses standard
microprocessor bus cycle timing. For sector unprotect, all
unprotected sectors must first be protected prior to the first
sector unprotect write cycle. The alternate method must be
implemented using programming equipment. The procedure
requires a high voltage (VID) on address pin A9 and the
control pins.
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.
Temporary Sector Unprotect
This feature allows temporary unprotection of previous
protected sectors to change data in-system. The Sector
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.
Unprotect mode is activated by setting the
During this mode, formerly protected sectors can be
programmed or erased by selecting the sector addresses.
pin to VID.
RESET
Hardware Data Protection
Once VID is removed from the
pin, all the previously
RESET
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.
protected sectors are protected again. Figure 1 shows the
algorithm, and the Temporary Sector Unprotect diagram
shows the timing waveforms, for this feature.
START
Write Protect (
)
WP
RESET = VID
(Note 1)
The Write Protect function provides a hardware method of
protecting the 16Kbytes of boot sector from erasure without
using VID
.
If the system asserts VIL on the
pin, the device disables
WP
erase function for the 16Kbyte boot sector (SA34 for the top
boot device and SA0 for the bottom boot device)
independently of whether those sectors were protected or
unprotected using the method described in Sector
Protection/Unprotection.
Perform Erase or
Program Operations
If the system asserts VIH on the
pin, the device reverts to
WP
whether the 16Kbyte boot sector was previously set to
protect or unprotected using the method described in Sector
Protection/Unprotection.
RESET = VIH
Low VCC Write Inhibit
Temporary Sector
Unprotect
Completed (Note 2)
When VCC is lower than VLKO, the device does not accept
any write cycles. This protects data during VCC power up
and power down. The command register and all internal
program/erase circuits are disabled, and the device resets.
Subsequent writes are ignored until VCC is greater than
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once again.
VLKO. The system must provide the proper signals to the
control pins to prevent unintentional writes when VCC is
greater than VLKO
.
Figure 1. Temporary Sector Unprotect Operation
Confidential
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Rev.1.0 July 2019
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
