24FC65T View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'24FC65T' PDF : 14 Pages View PDF
24FC65
2.0 FUNCTIONAL DESCRIPTION
The 24FC65 supports a bidirectional two-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 must be controlled
by a master device which generates the serial clock
(SCL), controls the bus access, and generates the
START and STOPs, while the 24FC65 works as slave.
Both master and slave can operate as transmitter or
receiver but the master device determines which mode
is activated.
3.0 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.
Accordingly, the following bus conditions have been
defined (Figure 3-1).
3.1 Bus not Busy (A)
Both data and clock lines remain HIGH.
3.2 Start Data Transfer (B)
A HIGH to LOW transition of the SDA line while the
clock (SCL) is HIGH determines a START. All
commands must be preceded by a START.
3.3 Stop Data Transfer (C)
A LOW to HIGH transition of the SDA line while the
clock (SCL) is HIGH determines a STOP. All operations
must be ended with a STOP.
3.4 Data Valid (D)
The state of the data line represents valid data when,
after a START, 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 and
terminated with a STOP. The number of the data bytes
transferred between the START and STOPs is
determined by the master device.
3.5 Acknowledge
Each receiving device, when addressed, is obliged 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 24FC65 does not generate any
acknowledge bits if an internal program-
ming cycle is in progress.
A device that acknowledges must 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.
During reads, 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 (24FC65) must leave the data line
HIGH to enable the master to generate the STOP.
FIGURE 3-1: DATA TRANSFER SEQUENCE ON THE SERIAL BUS
(A) (B)
SCL
(D)
(D)
(C) (A)
SDA
START
Condition
DS21125E-page 4
Address Data Allowed
or
to Change
Acknowledge
Valid
STOP
Condition
2004 Microchip Technology Inc.
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