TCA8418EYFPR datasheet(22/51 Pages) TI2

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SCL

SDA

MSB

Bit

LSB

Byte: 1010 1010 ( 0xAAh )

SDA line stable while SCL line is high

ACK

SCL

SDA

STAR T

Condition

STOP

Condition

Data Transfer

TCA8418E

SCPS222C – MAY 2010 – REVISED OCTOBER 2015

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Programming (continued)

–

Master-receiver terminates the transfer with a STOP condition.

Figure 22. Definition of Start and Stop Conditions

Figure 23. Bit Transfer

8.5.2 Bus Transactions

Data must be sent to and received from the slave devices, and this is accomplished by reading from or writing to

registers in the slave device.

Registers are locations in the memory of the slave which contain information, whether it be the configuration

information or some sampled data to send back to the master. The master must write information to these

registers in order to instruct the slave device to perform a task.

While it is common to have registers in I2C slaves, note that not all slave devices will have registers. Some

devices are simple and contain only 1 register, which may be written to directly by sending the register data

immediately after the slave address, instead of addressing a register. An example of a single-register device

would be an 8-bit I2C switch, which is controlled via I2C commands. Since it has 1 bit to enable or disable a

channel, there is only 1 register needed, and the master merely writes the register data after the slave address,

skipping the register number.

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