April 2001
FM25C040U
4K-Bit SPI™ Interface
Serial CMOS EEPROM
General Description
Functions
The FM25C040U is a 4K (4,096) bit serial interface CMOS
EEPROM (Electrically Erasable Programmable Read-Only
Memory). This device fully conforms to the SPI 4-wire protocol
whichusesChipSelect(/CS), Clock(SCK), Data-in(SI)andData-
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.
■ SPI MODE 0 interface
■ 4,096 bits organized as 512 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
This SPI EEPROM family is designed to work with the 68HC11 or
any other SPI-compatible, high-speed microcontroller and offers
both hardware (/WP pin) and software ("block write") data protec-
tion. For example, entering a 2-bit code into the STATUS REGIS-
TER prevents programming in a selected block of memory and all
Features
■ Sequential read of entire array
■ 4 byte "Page write" mode to minimize total write time per
byte
programming can be inhibited by connecting the /WP pin to VSS
;
allowing the user to protect the entire array or a selected section.
In addition, SPI devices feature a /HOLD pin, which allows a
temporary interruption of the datastream into the EEPROM.
■ /WP pin and BLOCK WRITE protection to prevent inadvert-
ent programming as well as programming ENABLE and
DISABLE opcodes.
■ /HOLD pin to suspend data transfer
Fairchild EEPROMs are designed and tested for applications
requiring high endurance, high reliability, and low power con-
sumption for a continuously reliable non-volatile solution for all
markets.
■ 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
Block Diagram
/CS
/HOLD
SCK
VCC
VSS
Instruction
Decoder
Control Logic
and Clock
/WP
Instruction
SI
Generators
Register
Program
Enable
Address
Counter/
Register
High Voltage
Generator
and
Program
Timer
VPP
Decoder
EEPROM Array
Read/Write Amps
Data In/Out Register
8 Bits
Data Out
Buffer
SO
Non-Volatile
Status Register
SPI™ is a trademark of Motorola Corporation
1
© 2001 Fairchild Semiconductor Corporation
FM25C040U Rev. A
www.fairchildsemi.com