Datasheet

PCA8575_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 21 March 2007 6 of 30
NXP Semiconductors
PCA8575
Remote 16-bit I/O expander for I
2
C-bus with interrupt
7. Functional description
Refer to Figure 1 “Block diagram of PCA8575”.
7.1 Device address
Following a START condition, the bus master must send the address of the slave it is
accessing and the operation it wants to perform (read or write). The address of the
PCA8575 is shown in Figure 9. Slave address pins AD2, AD1, and AD0 choose 1 of
8 slave addresses. To conserve power, no internal pull-up resistors are incorporated on
AD2, AD1, and AD0. Address values depending on AD2, AD1, and AD0 can be found in
Table 3 “PCA8575 address map”.
Remark: The General Call address (0000 0000b) and the Device ID address
(1111 100Xb) are reserved and cannot be used as device address. Failure to follow this
requirement will cause the PCA8575 not to acknowledge.
The last bit of the first byte defines the operation to be performed. When set to logic 1 a
read is selected, while a logic 0 selects a write operation.
When AD2, AD1 and AD0 are held to V
DD
or V
SS
, the same address as the PCF8575 is
applied.
7.1.1 Address map
Fig 9. PCA8575 address
R/W
002aab636
A6 A5 A4 A3 A2 A1 A0
programmable
slave address
Table 3. PCA8575 address map
A6 A5 A4 A3 A2 A1 A0 Address (hex)
010000020h
010000121h
010001022h
010001123h
010010024h
010010125h
010011026h
010011127h