Datasheet

PCA8574_PCA8574A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 3 — 3 June 2013 6 of 32
NXP Semiconductors
PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
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 (write operation is shown in
Figure 6
).
7.1.1 Address maps
The PCA8574 and PCA8574A are functionally the same, but have a different fixed portion
(A6 to A3) of the slave address. This allows eight of the PCA8574 and eight of the
PCA8574A to be on the same I
2
C-bus without address conflict.
Table 4. PCA8574 address map
Pin connectivity Address of PCA8574 Address byte value 7-bit
hexadecimal
address
without R/W
A2 A1 A0 A6 A5 A4 A3 A2 A1 A0 R/W Write Read
V
SS
V
SS
V
SS
0100000 - 40h 41h 20h
V
SS
V
SS
V
DD
0100001 - 42h 43h 21h
V
SS
V
DD
V
SS
0100010 - 44h 45h 22h
V
SS
V
DD
V
DD
0100011 - 46h 47h 23h
V
DD
V
SS
V
SS
0100100 - 48h 49h 24h
V
DD
V
SS
V
DD
0100101 - 4Ah 4Bh 25h
V
DD
V
DD
V
SS
0100110 - 4Ch 4Dh 26h
V
DD
V
DD
V
DD
0100111 - 4Eh 4Fh 27h
Table 5. PCA8574A address map
Pin connectivity Address of PCA8574A Address byte value 7-bit
hexadecimal
address
without R/W
A2 A1 A0 A6 A5 A4 A3 A2 A1 A0 R/W Write Read
V
SS
V
SS
V
SS
0111000 - 70h 71h 38h
V
SS
V
SS
V
DD
0111001 - 72h 73h 39h
V
SS
V
DD
V
SS
0111010 - 74h 75h 3Ah
V
SS
V
DD
V
DD
0111011 - 76h 77h 3Bh
V
DD
V
SS
V
SS
0111100 - 78h 79h 3Ch
V
DD
V
SS
V
DD
0111101 - 7Ah 7Bh 3Dh
V
DD
V
DD
V
SS
0111110 - 7Ch 7Dh 3Eh
V
DD
V
DD
V
DD
0111111 - 7Eh 7Fh 3Fh