Datasheet

Bus Transactions
Writes
SCL
Start Condition
Data 1 Valid
SDA
Write to Port
Data Out
From Port
R/W ACK From Slave ACK From Slave ACK From Slave
1 98765432
Data 11A2
0
0S 11 A1 A0 0 A 0000000 A A P
t
pv
Data to PortCommand ByteSlave Address
1/0A20 0S 11 A1 A0 0 A 0000000 A A P
SCL
SDA
Start Condition R/W
ACK From Slave ACK From Slave ACK From Slave
1
9
8765432
Data to RegisterCommand ByteSlave Address
Data
PCA9557
www.ti.com .................................................................................................................................................... SCPS133I – DECEMBER 2005 – REVISED JUNE 2008
Data is exchanged between the master and PCA9557 through write and read commands.
Data is transmitted to the PCA9557 by sending the device address and setting the least-significant bit (LSB) to a
logic 0 (see Figure 4 for device address). The command byte is sent after the address and determines which
register receives the data that follows the command byte. There is no limitation on the number of data bytes sent
in one write transmission (see Figure 6 and Figure 7 ).
Figure 6. Write to Output Port Register
< br/ >
Figure 7. Write to Configuration or Polarity Inversion Registers
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Product Folder Link(s): PCA9557