HY29LV800 Datasheet, PDF (20/40 Pages) Hynix Semiconductor – 8 Mbit (1M x 8/512K x 16) Low Voltage Flash Memory

HY29LV800
HARDWARE DATA PROTECTION
The HY29LV800 provides several methods of pro-
tection to prevent accidental erasure or program-
ming which might otherwise be caused by spuri-
ous system level signals during V_CC power-up and
power-down transitions, or from system noise.
These methods are described in the sections that
follow.
Command Sequences
Commands that may alter array data require a
sequence of cycles as described in Table 6. This
provides data protection against inadvertent writes.
Low V_CC Write Inhibit
To protect data during V_CC power-up and power-
down, the device does not accept write cycles
when V_CC is less than V_LKO (typically 2.4 volts). The
command register and all internal program/erase
circuits are disabled, and the device resets to the
Read mode. Writes are ignored until V_CC is greater
than V_LKO. The system must provide the proper
signals to the control pins to prevent unintentional
writes when V_CC is greater than V_LKO.
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#,
CE# or WE# do not initiate a write cycle.
Logical Inhibit
Write cycles are inhibited by asserting any one of
the following conditions: OE# = V_IL , CE# = V_IH, or
WE# = V_IH. To initiate a write cycle, CE# and WE#
must be a logical zero while OE# is a logical one.
Power-Up Write Inhibit
If WE# = CE# = V_IL and OE# = V_IH during power
up, the device does not accept commands on the
rising edge of WE#. The internal state machine is
automatically reset to the Read mode on power-
up.
Sector Protection
Additional data protection is provided by the
HY29LV800’s sector protect feature, described
previously, which can be used to protect sensitive
areas of the Flash array from accidental or unau-
thorized attempts to alter the data.
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Rev. 1.0/Nov. 01