General Description
The FM25C640U is a 64K bit serial interface CMOS EEPROM (Electrically Erasable Programmable Read-Only Memory). This device fully conforms to the SPI 4-wire protocol which uses Chip Select (/CS), Clock (SCK), Data-in (SI) and Data-out (SO) pins to synchronously control data transfer between the SPI microcontroller and the EEPROM. In addition, the serial interface allows a minimal pin count, packaging designed to simplify PC board layout requirements and offers the designer a variety of low voltage and low power options.

FEATUREs
■ Sequential read of entire array
■ 32 byte "Page write" mode to minimize total write time per byte
■ /WP pin and BLOCK WRITE protection to prevent inadvertent programming as well as programming ENABLE and DISABLE opcodes.
■ /HOLD pin to suspend data transfer
■ Typical 1µA standby current (ISB) for "L" devices and 0.1µA standby current for "LZ" devices.
■ Endurance: Up to 1,000,000 data changes
■ Data retention greater than 40 years

Functions
■ SPI MODE 0 interface
■ 64K bits organized as 8K x 8
■ Extended 2.7V to 5.5V operating voltage
■ 2.1 MHz operation @ 4.5V - 5.5V
■ Self-timed programming cycle
■ "Programming complete" indicated by STATUS REGISTER polling
■ /WP pin and BLOCK WRITE protection