24C02CT Datasheet, PDF (5/28 Pages) Microchip Technology – 2K 5.0V I2C Serial EEPROM

24C02C
4.0 BUS CHARACTERISTICS
The following bus protocol has been defined:
• Data transfer may be initiated only when the bus
is not busy.
• During data transfer, the data line must remain
stable whenever the clock line is high. Changes in
the data line while the clock line is high will be
interpreted as a Start or Stop condition.
Accordingly, the following bus conditions have been
defined (Figure 4-1).
4.1 Bus Not Busy (A)
Both data and clock lines remain high.
4.2 Start Data Transfer (B)
A high-to-low transition of the SDA line while the clock
(SCL) is high determines a Start condition. All
commands must be preceded by a Start condition.
4.3 Stop Data Transfer (C)
A low-to-high transition of the SDA line while the clock
(SCL) is high determines a Stop condition. All opera-
tions must be ended with a Stop condition.
4.4 Data Valid (D)
The state of the data line represents valid data when,
after a Start condition, the data line is stable for the
duration of the high period of the clock signal.
The data on the line must be changed during the low
period of the clock signal. There is one bit of data per
clock pulse.
Each data transfer is initiated with a Start condition and
terminated with a Stop condition. The number of the
data bytes transferred between the Start and Stop
conditions is determined by the master device and is
theoretically unlimited, although only the last sixteen
will be stored when doing a write operation. When an
overwrite does occur it will replace data in a first-in first-
out fashion.
4.5 Acknowledge
Each receiving device, when addressed, is required to
generate an acknowledge after the reception of each
byte. The master device must generate an extra clock
pulse, which is associated with this Acknowledge bit.
Note:
The 24C02C does not generate any
Acknowledge bits if an internal
programming cycle is in progress.
The device that acknowledges has to pull down the
SDA line during the Acknowledge clock pulse in such a
way that the SDA line is stable low during the high
period of the acknowledge related clock pulse. Of
course, setup and hold times must be taken into
account. A master must signal an end of data to the
slave by not generating an Acknowledge bit on the last
byte that has been clocked out of the slave. In this
case, the slave must leave the data line high to enable
the master to generate the Stop condition (Figure 4-2).
FIGURE 4-1:
SCL ^{(A) (B)}
DATA TRANSFER SEQUENCE ON THE SERIAL BUS CHARACTERISTICS
(C)
(D)
(C) (A)
SDA
Start
Condition
Address or
Acknowledge
Valid
Data
Allowed
to Change
FIGURE 4-2:
ACKNOWLEDGE TIMING
Acknowledge
Bit
SCL
12 345678 9 123
Stop
Condition
SDA
Data from transmitter
Transmitter must release the SDA line at this point
allowing the Receiver to pull the SDA line low to
acknowledge the previous eight bits of data.
Data from transmitter
Receiver must release the SDA line at this point
so the Transmitter can continue sending data.
© 2008 Microchip Technology Inc.
DS21202H-page 5