X28HC256 pdf datasheet (5V, By

The X28HC256 is a second generation high performance
CMOS 32k x 8 EEPROM. It is fabricated with Intersil’s
proprietary, textured poly floating gate technology, providing
a highly reliable 5V only nonvolatile memory.
The X28HC256 supports a 128-byte page write operation,
effectively providing a 24μs/byte write cycle, and enabling
the entire memory to be typically rewritten in less than 0.8
seconds. The X28HC256 also features DATA Polling and
Toggle Bit Polling, two methods of providing early end of
write detection. The X28HC256 also supports the JEDEC
standard Software Data Protection feature for protecting
against inadvertent writes during power-up and power-down.
Endurance for the X28HC256 is specified as a minimum
1,000,000 write cycles per byte and an inherent data
retention of 100 years.