24LC08B Datasheet, PDF (4/12 Pages) Microchip Technology – 8K/16K I 2 C ™ Serial EEPROMs in ISO Micromodules

24LC08B/16B MODULES
2.0 PAD DESCRIPTIONS
2.1 SDA (Serial Data)
This is a Bi-directional 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 VCC (typical 10Ω).
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 condi-
tions.
2.2 SCL (Serial Clock)
This input is used to synchronize the data transfer from
and to the device.
3.0 FUNCTIONAL DESCRIPTION
The 24LC08B/16B supports a Bi-directional 2-wire bus
and data transmission protocol. A device that sends
data onto the bus is defined as transmitter, and a
device receiving data as receiver. The bus has to be
controlled by a master device which generates the
serial clock (SCL), controls the bus access, and gener-
ates the START and STOP conditions, while the
24LC08B/16B works as slave. Both, master and slave
can operate as transmitter or receiver but the master
device determines which mode is activated.
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 5-2).
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 condi-
tion.
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
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 clock pulse per
bit of data.
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 16
will be stored when doing a write operation. When an
overwrite does occur it will replace data in a first in first
out fashion.
DS21224A-page 4
© 1997 Microchip Technology Inc.