24AA00/24LC00/24C00
2.0
2.1
PIN DESCRIPTIONS
SDA Serial Data
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).
This is a bidirectional pin used to transfer addresses
and data into and data out of the device. It is an open
drain terminal, therefore the SDA bus requires a pull-up
resistor to V
CC
(typical 10 kΩ for 100 kHz, 2 kΩ for
400 kHz).
For normal data transfer SDA is allowed to change only
during SCL low. Changes during SCL high are
reserved for indicating the Start and Stop conditions.
2.2
SCL Serial Clock
4.1
Bus Not Busy (A)
This input is used to synchronize the data transfer from
and to the device.
Both data and clock lines remain high.
4.2
Start Data Transfer (B)
2.3
Noise Protection
The SCL and SDA inputs have Schmitt Trigger and
filter circuits which suppress noise spikes to assure
proper device operation even on a noisy bus.
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)
3.0
FUNCTIONAL DESCRIPTION
The 24XX00 supports a bidirectional 2-wire bus and
data transmission protocol. A device that sends data
onto the bus is defined as a transmitter, and a device
receiving data as a receiver. The bus has to be
controlled by a master device which generates the
Serial Clock (SCL), controls the bus access, and
generates the Start and Stop conditions, while the
24XX00 works as slave. Both master and slave can
operate as transmitter or receiver, but the master
device determines which mode is activated.
A low-to-high transition of the SDA line while the clock
(SCL) is high determines a Stop condition. All
operations 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.
DS21178G-page 4
©
2007 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
