IS24C32A
®
IS24C64A/B
ISSI
DEVICE OPERATION
Stop Condition
IS24C32A/64A/64B features serial communication and
supports a bi-directional 2-wire bus transmission protocol.
The Stop condition is defined as a Low to High transition of
SDAwhenSCLisHigh. AlloperationsmustendwithaStop
condition.
2-WIRE BUS
Acknowledge (ACK)
Thetwo-wirebusisdefinedasaSerialDataline(SDA),and
a Serial Clock line (SCL). The protocol defines any device
that sends data onto the SDA bus as a transmitter, and the
receiving devices as a receiver. The bus is controlled by a
Master device that generates the SCL, controls the bus
access, andgeneratestheStopandStartconditions. The
IS24C32A/64A/64B is the Slave device on the bus.
After a successful data transfer, each receiving device is
required to generate an ACK. The Acknowledging device
pulls down the SDA line.
Reset
The IS24C32A/64A/64B contains a reset function in case
the 2-wire bus transmission is accidentally interrupted
(eg. a power loss), or needs to be terminated mid-stream.
The reset is caused when the Master device creates a
Start condition. To do this, it may be necessary for the
Master device to monitor the SDA line, which may cycle
the SCL up to nine times. (For each clock signal
transition to High, the Master checks for a High level on
SDA.)
The Bus Protocol:
– Data transfer may be initiated only when the bus is not
busy
– During a data transfer, the data line must remain stable
whenevertheclocklineishigh. Anychangesinthedata
line while the clock line is high will be interpreted as a
Start or Stop condition.
Standby Mode
The state of the data line represents valid data after a Start
condition.Thedatalinemustbestableforthedurationofthe
High period of the clock signal. The data on the SDA line
may be changed during the Low period of the clock signal.
Thereisoneclockpulseperbitofdata. Eachdatatransfer
isinitiatedwithaStartconditionandterminatedwithaStop
condition.
Power consumption is reduced in standby mode. The
IS24C32A/64A/64Bwillenterstandbymode: a)AtPower-
up, and remain in it until SCL or SDA toggles; b) Following
the Stop signal if a no write operation is initiated; or c)
Followinganyinternalwriteoperation.
Start Condition
The Start condition precedes all commands to the device
andisdefinedasaHightoLowtransitionofSDAwhenSCL
isHigh.TheEEPROMmonitorstheSDAandSCLlinesand
will not respond until the Start condition is met.
Integrated Silicon Solution, Inc. — 1-800-379-4774
ADVANCEDINFORMATION Rev. 00A
3
01/26/04
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
