MYXX28HC256 Datasheet, PDF (6/23 Pages) Micross Components – No External High Voltages or VPP

256Kb EEPROM
MYXX28HC256
Hardware Data Protection
The MYXX28HC256 provides two hardware features that protect
nonvolatile data from inadvertent writes.
• Default V_CC Sense - All write functions are inhibited when V_CC is
≤ 3.5V Typically.
• Write Inhibit - Holding either OE# LOW, WE# HIGH, or CE# HIGH
will prevent an inadvertent write cycle during power-up and
power-down, maintaining data integrity.
can be automatically protected during power-up and power-down
without the need for external circuits by employing the software
data protection feature. The internal software data protection
circuit is enabled after the first write operation utilizing the software
algorithm. This circuit is nonvolatile and will remain set for the life of
the device unless the reset command is issued.
Once the software protection is enabled, the MYXX28HC256 is also
protected from inadvertent and accidental writes in the powered-up
state. That is, the software algorithm must be issued prior to writing
additional data to the device.
Software Data Protection
Software Algorithm
The MYXX28HC256 offers a software controlled data protection
feature. The MYXX28HC256 is shipped from Micross with the
software data protection NOT ENABLED; that is, the device will
be in the standard operating mode. In this mode data should be
protected during power-up/down operations through the use of
external circuits. The host would then have open read and write
access of the device once V_CC was stable. The MYXX28HC256
Selecting the software data protection mode requires the host
system to precede data write operations by a series of three write
operations to three specific addresses. Refer to Figure 9 and 10
for the sequence. The three-byte sequence opens the page write
window enabling the host to write from one to one hundred twenty-
eight bytes of data. Once the page load cycle has been completed,
the device will automatically be returned to the data protected state.
MYXX28HC256
Revision 1.4 - 02/13
6