TCA9545A Datasheet, PDF (13/30 Pages) Texas Instruments – Low Voltage 4-channel I2C and SMbus Switch With Interrupt Logic and Reset Functions

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Programming (continued)
TCA9545A
SCPS204B – JANUARY 2014 – REVISED MARCH 2014
SDA
SCL
S
P
Start Condition
Stop Condition
Figure 9. Definition of Start and Stop Conditions
A device generating a message is a transmitter; a device receiving a message is the receiver. The device that
controls the message is the master, and the devices that are controlled by the master are the slaves (see
Figure 10).
SDA
SCL
Master
Transmitter/
Receiver
Slave
Receiver
Slave
Transmitter/
Receiver
Master
Transmitter
Master
Transmitter/
Receiver
I²C
Multiplexer
Slave
Figure 10. System Configuration
The number of data bytes transferred between the start and the stop conditions from transmitter to receiver is not
limited. Each byte of eight bits is followed by one acknowledge (ACK) bit. The transmitter must release the SDA
line before the receiver can send an ACK bit.
When a slave receiver is addressed, it must generate an ACK after the reception of each byte. Also, a master
must generate an ACK after the reception of each byte that has been clocked out of the slave transmitter. The
device that acknowledges must pull down the SDA line during the ACK clock pulse so that the SDA line is stable
low during the high pulse of the ACK-related clock period (see Figure 11). Setup and hold times must be taken
into account.
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