TCA8418E_15 Datasheet, PDF (22/50 Pages) Texas Instruments – I2C Controlled Keypad Scan IC With Integrated ESD Protection

TCA8418E
SCPS222C – MAY 2010 – REVISED OCTOBER 2015
Programming (continued)
– Master-receiver terminates the transfer with a STOP condition.
SCL
SDA
ST AR T
Condition
Data Transfer
STOP
Condition
Figure 22. Definition of Start and Stop Conditions
SDA line stable while SCL line is high
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SCL
1
0
1
0
1
0
1
0
ACK
SDA
MS B
Bit
Bit
Bit
Bit
Bit
Bit
LSB
ACK
Byte: 1010 1010 ( 0xAAh )
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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