SPI Serial EEPROM

The 25Cxxx serial electrically-erasable programmable read only memory (EEPROM). 
The device is optimized for use in many industrial and commercial applications
where low-power and low-voltage operation are essential. 
The device is enabled through the Chip Select pin (CS) and accessed via a
3-wire interface consisting of 
Serial Data Input (SI), 
Serial Data Output (SO), 
and Serial Clock (SCK). 
All programming cycles are completely self-timed, and no separate ERASE cycle is required before WRITE.

BLOCK WRITE protection is enabled by programming the status register with top 1/4, top 1/2 
or entire array of write protection.
Separate program enable and program disable instructions are provided for additional 
data protection. 
Hardware data protection is provided via the WP pin to protect against inadvertent 
write attempts to the status register. 
The HOLD pin may be used to suspend any serial communication without resetting the serial sequence.