TCA9555_16 Datasheet, PDF (18/46 Pages) Texas Instruments – Low-Voltage 16-Bit I2C and SMBus I/O Expander with Interrupt Output and Configuration Registers

TCA9555
SCPS200D – JULY 2009 – REVISED JULY 2016
Programming (continued)
Figure 24 and Figure 25 show the general procedure for a master to access a slave device:
1. If a master wants to send data to a slave:
– Master-transmitter sends a START condition and addresses the slave-receiver.
– Master-transmitter sends data to slave-receiver.
– Master-transmitter terminates the transfer with a STOP condition.
2. If a master wants to receive or read data from a slave:
– Master-receiver sends a START condition and addresses the slave-transmitter.
– Master-receiver sends the requested register to read to slave-transmitter.
– Master-receiver receives data from the slave-transmitter.
– Master-receiver terminates the transfer with a STOP condition.
SCL
SDA
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ST AR T
Condition
Data Transfer
STOP
Condition
Figure 24. Definition of Start and Stop Conditions
SDA line stable while SCL line is high
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 25. Bit Transfer
18
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